Sorry to see the roller coaster in an infinite loop. Years ago I knew someone doing his xw this way. He was working for his folks in a carpet company ... for cash, no records. They also bought the house he and his new gal moved into while he wasn't helping his x and three sons.
There is justice. He burned down the new house his parents bought with a plumbing torch, accident. His xw found out the hard way that he had not paid income taxes for the years he was married, and the IRS began taking away the house his w kept in the settlement. They said he had no money and she got half the liability for his taxes in her d. She worked a deal to pay up over time, and they deferred snatching the house till the kids were 18. Luckily, she finally settled with IRS and now owns the house. Her shiftless xh never ever held a job that could get garnished. Piece of Sh!t
Anyway, you need to talk to your L about the possibility that your jerk's uncle is helping him hide salary and associated taxes. THAT is a Federal no-no for both of them. I heard the IRS is giving rewards to people reporting tax cheats! Maybe your L has some ideas of how to metion this just right, in court - or have uncle brought in under oath to explain the big pay cut letter ... with an audited set of books!
You've survived some of the craziest there are and you've done great. It may be hard to believe right now but I am sure you will find your way through this also.