The rear locker splines are corser and seem to always take longer to lock. Try locking the rear and do slow figure 8s in the dirt to see if it'll lock in.
The mobile app has quit on my phone today, also can't get there through taptalk. I can open in the mobile browser. Is anything going on, or do you think it might just be my phone.
Just my thoughts but I would do some more checking before I got to far in. Like pull and check #6 plug has it been steam cleaned, do a compression test, check for bubbles in the overthrow, pressure test the cooling system. It it is bad I would vote on getting a beater car. Take your time and...
There should be a wire harness at the left rear piller area, that is for the third dome light. Not sure what year yours is but. it was there or just under the headliner on my 94.
If you have not ruled out the module for the trailer lights I would do that before I would start cutting up your wire harness. It's just a matter of disconnect 2 plugs near the jack and 2 more behind the pass side rear panel. This will take only about 5 min, and will eliminate a aftermarket...
If you take off the DS rear panel you will see the latch that works the door. I had this problem a couple months ago. My cable had rubbed the protective coating under the rear scuff plate causing my cable to rust. So I ended up having to replace it.