No spark I Install new distributor?

Battery power goes to the + side of the coil. The - side is the trigger. The ignition box has a three wire plug that goes to the inductive pick-up in the distributor. That is the trigger that tells the box when to fire. Then there is the second plug that carries power and a timing signal. It is a 3 part system. The box, distributer and coil work together. Test for power at the positive post on the coil, Then at the 2 wire plug to the ignitor box. (Should be a Red wire with black stripe, but there were a few colors used, just like the ignition boxes. If you have power to those with the key on, then the key switch is working. However with the vehicle doing nothing when you turn the key, ignition isn't the problem, the power isn't getting through so we need to figure that out first, If you just want to see if the engine will run and jumping the solenoid gets it to turn over you could try an old trick. Take a length of wire, connect it to the power feed on the ignition box, then another to the positive terminal on the coil. Now jump the solenoid and see if it starts up. You cannot drive it this way because the constant 12 volts could burn out the coil and nothing else is going to work, but it should let you test the engine. To shut it off disconnect the wire to the battery.

There should not be 12 volts on the negative side, that points to something wired wrong or the ground side of the battery isn't connected very well. I would start there, Not having a good ground path may be causing all of these issues and can do a lot of damage to other parts. So start at the battery, remove the cables clean them. Re-connect, repeat at each point they connect. Check the engine to chassis ground and the battery to frame and chassis grounds. Here is another simple test called a voltage drop test. Take your meter and set it to 20 volts or so. Now turn on something that draws power, headlights brake lights or similar. Now take the probes and connect one to battery positive, then to the battery connection on the fuse box, you should see close to zero volts. Now check the negative side by touching the battery negative post with one lead and the engine block with the other, Same thing here, you should see close to zero. Same from battery negative to any ground point on the truck. It's a fast way to see if there is a bad cable or connection, I have done this test on a no start vehicle and discovered that all of the current from the battery was being stopped at the point where the battery cable bolted to the clamp on the battery post. Because you have basically lost all power for starting and ignition you might find the bad connection this way.

The negative side is the trigger on the coil. The ignition works by grounding that side and then opening it, when it opens the magnetic field collapses and you get a spark. No way to check for the signal without an oscilloscope. The missing ground strap is part of the problem. You should have one negative cable from the negative side of the battery going to the engine block, then a second cable from the engine block to the firewall. Then another that goes from the negative to the body. And usually underneath there will be a cable connecting the cab to the box and another from the frame to the body. The ignition module for example has to be mounted and secured to have a ground, if you just plug it it without a good ground it will burn it out because of the lack of grounding.
The "spark" at the solenoid also indicates a poor connection. From the descriptions so far I would start there, don't even bother with the ignition or starter until you go through the connections and ensure they are all clean and tight, Then do the voltage drop test, it is possible to have a cable that looks find but actually is damaged internally.

Backfiring can be timing or incorrect plug wire sequence. To install it correctly, pull all the spark plugs (makes rotating and setting it at TDC much easier. Now pull the distributor cap off, Rotate the engine until you get to top dead center on cylinder one. An easy way to tell is to put a finger or similar in the plug opening and listen and feel for the air pressure to increase as it comes up on compression. Now look on the damper and you should see a mark, line that up with the TDC point on the timing tab. Next set the distributor so the rotor lines up with the number one post on the cap. Then try to set it into place. Note how far the rotor moved, remove it and rotate the rotor back the same amount to the opposite side of the #1 plug wire post, now set it back in and if done correctly the rotor will turn and once seated it will all line up at TDC, Then clamp it in place. Now start it up and do the baseline timing using a light to set it to the spec for the engine you have.

Make sure the distributor is installed correctly, then verify the plug wires are in the correct order and check the base timing as stated in my earlier post. Did you get it to turn over with the key now?

If you look up the VIN number online it might tell you what the engine is. Without that info the rest of your question cannot be answered correctly. Except for the question of finding TDC. You can do it the way I posted above, remove the plugs then rotate it while feeling for the compression to push out of the plug hole. Then you can set the distributor. No reason to open the engine.
Once that is done you can set the firing order as it is different for the engine types.
So look at the 4th digit in the VIN to find the engine series (IF it is the original engine) VIN G = 302, VIN H = 351, VIN S = 400 and VIN J is the 460. The firing order you have is correct for the 302, the 400 and the 460 engines however the 351 uses 1-3-7-2-6-5-4-8. Then look at the chart I attached and find the engine and the proper timing.

OOF, not a good thing, The misfiring is likely that the timing is still off a bit, adjust it using a timing light, The oil pouring out the back is not a good thing, it means the rear main seal has failed. On that engine design it means the bottom end of the engine has to come apart for it to be replaced. What I suggest is getting a paper service manual for that truck. Then use that to go through the engine. If the rest of the truck is in good shape. Or see if you can get a crate engine to fit it if a rebuild is more than you want to do.

If it's leaking like that it's damaged and has to be replaced. Stinks but has to be done.

It's possible it is defective, it's also possible it was damaged on install or that there is something wrong on the crankshaft allowing it to leak. No way to tell until you can remove it and check the parts. Please ask the question about the starting issue as a different question, we try to keep issues as separate questions to make later searches easier.