I have several concerns, comments, and ideas, not the least of which being an alleged college student thinks this:
Now it's a fully rebuilt start so I don't know if this is part. Of the problem..
Is proper use of grammar and punctuation. Frankly with sentence structure like that you should be sent back to 5th grade.
Next, you said the starter is rebuilt, but from there it seems from what you have posted you assume it is good, no further questions. Have you bench tested it and seen that the bendix is kicking out correctly?
Also, while inspecting the teeth of the flywheel have you spun the engine around by hand to see all of them? This is another point which you have not specifically addressed. I have replaced a number of flywheels and flex plates over issues like this. Each one of them was perfectly OK on about 90% of the teeth, and then there was one area that was chewed so badly the starter couldn't catch very well.
Next item, do you have an auto or a manual? The flex plates on the early Colgone engines, even up through the late 90s, has issues with breaking.
Finally, if you are a college student I am assuming, though I may be wrong, that you are roughly 18-25 years old. The truck is older than you in human years, and car years are rougher than dog years, and the 2.8 was never a power house in the first place. At that age you probably have low compression, worn lifters (they are solid, not rollers) possibly worn push rods, and since you go to school in Ohio you may or may not have a student body who's African American component thinks that the cafeteria menu is racist for not including enough fried chicken based offerings.
Buying a GM is like violence, it's not the answer man. You have an old, worn out engine. These things happen. I think rather than throw your hands up in the air and call it junk because it wore out after 31 years, maybe you should stop to think that most vehicles built back then didn't have the wearwithal to last 31 years, and none of the vehicles being made today, even GMs, will be around in another 31 years, but I am willing to bet there will still be a few 80s Rangers kicking in 2047.