Transmission slipping?

There is no such thing as being to safe.
The only problem that I can see is that a fuse is made to protect a circuit. When you make the battery to solenoid test, you are making a complete circuit. The components in this circuits can only handle so much amperage.
I thought about whether the second fuse would be additive to the first or not. Meaning your hot leas has 30 Amp and negative has 10 Amp. The total may be 40 Amps.
Covertly, the smaller fuse is the weakest link and it will blow even under expected load if it is too small.

I think having the fuse on the hot lead is good enough.
I have tested stuff without using any fuses and depended on the fuses in the car to blow to save circuit.

So, stick with the inline on the hot wire/

If you got the other 2 solenoids to to test correctly, I think you should be confident.
You have the technique and guidance and I can tell that uou are very thorough.
You pulled information from here and Hayne's, used 2 multi-meters to account for accuracy and made the test wires properly. Are you an Engineering student, if not you should be.

Check on th eprice of the solenoid. Part of Electro-Mechanical diagnosis is hit or miss. It might be part of the problem. The only way you will know is to buy one.
Check prices at Roackauto. Com and USAutoparts. Com.
Rockauto has closeouts and you have to live without a warranty but you can get name brand stuff for unbelievable prices. They will still take returns if there is an issue.

Electrical diagnosis is really hard because parts fail slowly or intermitantly. Sometimes you have to wait for them to fail completely befoere you can diagnose the issue and then the part failure may cause other damage.
It is a process of elimination.
The tests are nearly the same except for resitance values. If you have checked the passage of the solenoid and it does not click every time you apply 12V, it fails the test and is working intermitantly. It does not follow the behaviour of the other solenoids as they reacted to the 12V application every time.
I think it is a problem as you said your transmission shifts properly sometimes, the solenoid works properly sometimes.
It may not be the problem, but it is failing and you can eliminate it from the list of possibilities.
I would replace it as automatic transmissions can get damaged when they do not shift properly.
I think you have good mechanical intuiton which is very thorough, you just need to be confident in your findings.
You are replicating what happens to that solenoid under normal operation. The only difference is that the voltage signal comes from the connector.
Check out prices and wheigh the risk. They always say, "$100 in maintenance saves $1000 in repair". Oh so true.

A really good set of tools for that is to get a set of dental type cleaning tools. Most auto parts stores have them and are often in their bargain bin.
They work great on getting small seals out too.
Also, get some silicone spray. Anytime you need to get rubberseals or palastic apart or protect it, it is what you want to use.
So, spray the connector with silicone spray.
Some connectors can be deceiving. When some connectors need the locking tabs pushed in to release, others may need to have it pushed out to release. You have to look at the connector and always be gentle. Try both ways if you are not sure. Using the dental tools really helps to probe into the connector and see which way the clip needs to be pushed to unlock the connector.
If you happen to break the connector or strip off the terminals. Hot Rod and high performance shops, or go to summitracing. Com, sell connector ends that are weatherproof. You just get terminals that match, they will have them or Radio Shack is good. Then get a good pair of elctrical plyers to strip wires and crimp terminals on wire. Then you have a new connector that you know how to dis-connect. They are not a lot of money either. I think I have seen some at NAPA.

I tried to send you this message once, but it looks like it did not make it, sorry if it is duplicate.

As far as the Transmission Range Sensor, I could only find one reference for which I sent you a location diagram. It seemed to otherwise be/or be part of the *****r position switch.

I sent you a voltage pin test chart. You can test a circuit or circuits in a component several ways to test them. Voltage gives you a value while continuity is either open/closed. So, if something that you test is nearly out of the specification range, it is probably slowly failing or internitantly failing. So, I think it will be an interesting test, let me know what comes of it.
I had to send you some diagrams in 2 part top and bottom pieces as they are too small to be usefule otherwise.
As far as the gear shifter, I sent you the locations of the shift solenoid lock and shifter lockout and the gear shift selector on the transaxle. I think you can take the cover off the shifter switch on the transaxle and slect gear by hand.

I wish I had a better answer about the range snesor, so I am sneding you everything I could find in relation to it.

Enjoy! I hope it gets you a few steps closer to your goal. Sounds like you are doing great and are good at getting as many information sources as possible. That is good as even the best information, except for 2carpros, can be different or mis-leading, etc.
Consider joining an on-line enthuisiast forum as you will find people who have been where you are now and can answer some questions I can't since I have not worked on your particular situation, always had manual tranny Hondas/Acura, and you may find that there are things that are not published anywhere are available through fellow Honda lovers. Honda-Tech. Com is a good one and I am a member. I hardley have time to go anymore, but they also have newparts reviews vendor reviews and used parts sales.
Take Care.

Your welcome.

They are saved as. Jpegs, so you can double click on the and then right click and either save to a folder and print, so you can preview first, or print straight from image. Being that it is a. Jpeg, I save them that way on purpose, makes them easy to print and you don't need any special software to view or print.
If you do have any printing problems, let me know because you should save them for future reference and you have to have a printout to refernce when you are working on your car.
The company pays to rights for the information. I am not sure if I am supposed to say where from, I know that sounds wierd but I really don't know and don't want to find out the hard way.
It does have some missing links as we have experienced but the diagrams are great to have and you cannot get them without paying for them. The only problem is that it has to be captured via screenshot software, scaled, etc. That is why I have to break some diagrams in half just so the text is big enough to read as formatting is unavailable on screenshots.
It is really nice if you have a color printer as they are colored diagrams, some of them.
The ones I split you would have to print out and cut with scissors and match up the top and bottom and then tape them together to have a one page diagram. I tried to keep more of what you needed in the first screenshot.
Let me know if they printout okay because I can save them as other file extensions and I could scale them, although it is in large increments only, to a different size.
I hope it gets you what you needed.

If your fluid is black then the clutches inside the transmission are burning up, causing the slipping. Changing the transmission will take care of it, or you can get it rebuilt. If you do get another transmission, (1) take a good look at the fluid before you buy it and (2) change the fluid. If the fluid is not red like it should be, walk away from it.

No problem. Let us know how it goes

Something is going wrong with the first gear and it could be electrical, mechanical or hydraulic. If the MIL is indicating, get a scan done to check for trouble codes. If no trouble codes are present, check fluid level and condition. Replace fluids if necessary and retry.

It could be an early sign of trouble but then again I have ever come across vehicles showing the same issues but are still on the road after a few years.

If there are trouble codes, it might give you some idea what could be wrong, usually electrical but if there are none, then just pray it does not give up till you are ready to give up on the vehicle.

There is nothing much you can do about it if it is mechanical and you can continue to use it till it fails. However if the symptoms becomes regular, that is when you should be prepared for it to fail.

In the meanwhile if the trans fluid had not ben replaced for some time, get it done. Always ensure the fluid level is correct and fluid quality is good.