No start

About the only thing you are missing is fuel injector action. So, to begin, check the "dedicated fuse #13" in the engine compartment relay center, left side under hood. It should be hot on both sides of the fuse all the time. If it is, and you have no voltage to the red wires at the fuel injectors with the key on run, try a new MFI relay or swap one in that will fit and the same type. It is located on that engine compartment relay center.
If you do have voltage to the injectors, then you must be missing the pulse, so check the ECM fuses. That may also be why you get a scan tool or code reader error not connecting. Check the "dedicated fuse #4" it powers the ECM. It is also in that engine compartment relay center. The other power feed is the same one as that "dedicated fuse #13" in the engine compartment relay center.

Yeah, the fuel pressure should be over 38 psi.
The fuse can blow if anything on that fuse's circuit is drawing too many amps. Or the fuse could have just been bad. If it never blows again, do not worry about it. If it blows again, first try a new MFI relay. If it still blows, then let me know cause then you will need to stick an ammeter into that fuse socket and see what the amp draw is then start disconnecting each item one at a time until the ammeter drops well below 20 amps.
Since there are so many things that fuse feeds you may want to start with retrieving trouble codes, once you get a tool to connect.

At first you said, "My machine gets no signal at all when hooked up. Very strange", now you say, "I have a Solus Pro Scanner but it says no codes. Weird.'
No signal is like a no communication but if it says no codes, then it is communicating, it is just that there are no codes.
If the fuel pump is on that fuse's circuit, that may indeed be the problem for both, not enough fuel pressure and also blowing the fuse, if the fuel pump is either shorted or the fuel pump power feed wire has a short and the fuel pump is not getting enough voltage.
Actually it is not on that same fuse.

The only thing it could be is spark plugs fouled with gasoline. Remove them all and either clean them off with some carburetor cleaner and let them dry or if they are old, just replace them and try the starting fluid again if it does not start up immediately.

That sounds like a short circuit within that engine compartment fuse relay box. They are all a direct feed right from the battery positive post. If just a few have no or low voltage and some have 12 volts, then obviously the power is making it to that box, it is just not making it all the fuse socket within the box. Most likely there is some shorted or melted parts inside that box.

No, some fuses only light up when the key is on start, but most of those fuses the key does not have to be on at all.
The ECU or PCM as it is called nowadays has a few power feeds. They are pin 66 a red/black wire, that comes from dedicated fuse #4 in the engine compartment relay box. Then there is pins 41 and 47, 2 red wires which are spliced together and come from that MFI relay and before that dedicated fuse #13.
They all should have 12 volts, with the key on run. Although the fuses are hot all the time with 12 volts.
Some of them you are checking at the PCM might be the ones that are only supposed to have 5 volts, like to power sensors. That may be why they appear low, but that is normal.

How are your fuel injectors getting voltage if that dedicated fuse #13 has no power?

I think we are talking about the wrong fuse #13.
There is a dedicated fuse #13 in the underhood relay center that is for the MFI relay and the fuel injectors, as well as the PCM and numerous sensors.
Then there is the multi-purpose fuse #13 in the junction box, behind left side of dash, that is for the malfunction indicator lamp. Is that the fuse #13 you are referring to or the one under the hood?

The fuse feeds the fuel pump relay and then the fuel pump relay feeds the fuel pump. There is no fuse in between the relay and the pump.

There is one other possibility since you said you have spark on all six cylinders, the compression is good, spark plugs are not gas fouled and it will not even start on starting fluid is that the firing order is wrong.
I see this has a distributor, and that firing order is simple to remember 123456, with #1 cylinder being on the front passenger side.

Oh, I see now that ECU, I thought you meant PCM. Sorry.
Okay, so back to no voltage at that #13 dedicated fuse under the hood. If there is no voltage to that fuse, then again how could your fuel injectors be hot?