2007 Tahoe, bad lifters, TBS, stabilitrac problems, rear differential....HELP!!

I have a 2007 Tahoe I bought used in 2013. It has ALWAYS had a faint ticking/tapping noise while idling and accelerating. Took it to 3 mechanics. All said it didn't sound like an issue worth pursuing as the high cost and lengthy time it would take. Fast forward 3 years and the tapping is slightly louder, but now theres intermittent stabilitrac disabled, traction control issues, etc. Follow the instructions in the owners manual and things seem fine. Then one day it throws a check engine light. Take it in have the code read, it says TBS Throttle body sensor is bad. Cool. All the forums I've read followed 19k different rabbit trails to all eventually end at the throttle body sensor being the root of the evil. Take it to the dealership. They say, no sorry. The sensor is fine. give me the truck back. fast forward 2 more years and the dashboard is lit up like a Christmas tree. Every dummy light is on. I take it to the dealership, ask it to be checked and have the oil changed. They called me back and said no they won't change the oil, because it has a bad lifter and there's no point. They don't even want to drop it off to me. In the same conversation the mechanic tries to convince me to sell my vehicle to anyone in his shop for $2500. I tell him no I love my truck I just need it fixed. Then he gives me an estimate. Calls me back 2 hours later and says the estimate is only for 1 lifter, i might need more they won't know until they open the engine. Then when I finally get it back, they have AFM listed with over $600 in cost. Saying it's necessary when this kind of job is done. But the Chevy employed master tech that I'm related to said no. Now it has been several weeks, I can't drive the vehicle because I don't want to destroy it but I can't afford a $1700 job to maybe fix the problem. Especially when I've read hundreds of things like this talking about chasing issues for months and costing thousands. For what?
And now the dealership is sending me mailings and calling my phone repeatedly trying to convince me to sell them my truck instead of fix it because they need used vehicles. Is this a joke? Thousands of consumers are getting screwed by purchasing vehicles that GM knows have problems, then the dealerships service departments try to get the thing back so they can sell it again?
Don't these people realize if I don't have $2000 to fix it I certainly can't afford a freaking payment on a new vehicle so i can help them out?!?!
Who's going to help ME out? We're a one income military family stuck with a turd vehicle that no one can even decide what the actual problem is!?!
What am I supposed to do now?!