Neutral safety switch

Remove the starter relay, then test for twelve volts on the terminals in the socket. A test light will be more accurate for this than a digital voltmeter.

You should find zero volts on all four terminals. Have a helper hold the ignition switch in the "crank" position. Now you should find twelve volts on two terminals. Shift to "reverse" or "drive". The twelve volts should be lost on one of those two terminals. That is the one coming from the neutral safety switch.

You can release the ignition switch. For the two remaining terminals, move the test light's ground clip to the battery's positive post. We will be checking for good ground circuits. Probe those last two terminals. The test light should light up on both of them. One is just reading through the relay's ground circuit. The other is reading through the starter solenoid, then to ground.

Up to now we do not even have to know which terminal is which. I expect you will find one of those four terminals did not read correctly. Tell me which one, and I will figure out where to go next.

I have my doubts, but you didn't list any symptoms for me to analyze. The tests I described cover all four parts of the circuit with just those four readings. If they all appear to be okay, two more tests at the starter will pinpoint the cause of a failure of the starter to crank the engine. There would be two different symptoms / observations as to the clunks or other noises that are heard when turning the ignition switch to "crank".

I'll be out of town at an old car show swap meet this weekend, so don't panic if I don't get back you to see how you're doing until next Monday night.

Happy to hear it's solved.

For the oil leak, if it's relatively slow, wash the area with Engine Degreaser, then add a small bottle of dark purple dye to the oil. Check a day later with a black light. The dye will show up as a bright yellow stain that you can follow back to the source. Auto parts stores will have the dye for the fluid being tested, and those that rent or borrow tools should have a black light.

This could be a number of things. However, the most important question is has the battery been replaced since you found it only had 7 volts or have you been trying to charge it or just let it run.

We need to start with having the battery load tested because if it is not able to hold a charge then it needs to be replaced. This could be all your issues but if something is draining the battery then we need to test the draw.

Here are a couple of guides that help with this. Let us know this info and we can go from there. However, we need to get a new post started because this issue is not going to be related to this post and we need to keep each one to one topic. So if you can get it tested and post those results with this info to a new post, we will jump on it.
Thanks

https://www.2carpros.com/articles/car-battery-load-test

https://www.2carpros.com/articles/car-battery-dead-overnight

https://www.2carpros.com/questions/new