@freedomfighter That's really a shame that Illinois is set up like that. In Texas you can have your child sign an Affidavit and their preference can be considered once he/she turns 12 years old. It doesn't mean the judge will agree necessarily. It's the first bullet point from a case called Holley vs. Adams, that lists what is in the Best Interest of the Child. A child's preference speaks volumes if it is coming from a place of honesty and there is no alienation. I know you said you read online that Illinois allows the kid to choose at 18. But that doesn't mean the child can't be heard by the Judge in chambers to have their preference considered if he/she is old enough and mature enough. You should consult a lawyer about that. There are quite a few lawyers who give you 30 minutes for free.
One thing you can try is just start representing yourself in court. It's called "Pro Se." The cost of litigating is paying the lawyers. Court filing fees are peanuts compared to that. Check out a YouTube channel called "The Proper Person" Alex Falconi puts out regular videos talking about different aspects of how to represent yourself. He's in Nevada but many of the logistics are similar across states. He went from having supervised visits to getting his Ex's parental rights terminated and sole custody over his son. It's kind of amazing. He could not use lawyers. It would have been way too expensive and he was up against an Ex wife who had family members bankrolling her case. Another thing you can do is to make use of the free legal clinics in your area. There are lawyers (usually fresh out of law school) who will take your case at no charge just to get the experience.
We have been systematically documenting, keeping communications to email, recording, and setting more and more boundaries, We do not allow anything unless it is spelled out in the Custody document. Whereas before the bad behavior and shenanigans we tried to be flexible and work with our Ex. We are pursuing legal action but as we've neared closer to hiring a lawyer, getting the papers served, etc... The Ex has started behaving 200% better. People will sense the change and start worrying about what you are up to you when you do things like what I just listed.
There are other things that you can do involving setting boundaries. I know it must seem impossible when these things are occurring during your Ex husband's parenting time. Most of the boundaries you set really have to be for things that happen on your own time and he pulls stuff. Here's just a few things I can think of off the top of my head from your list:
Do not send them to Dad's with any money. If it is money Dad is giving them and then taking there isn't much you can do about that.
Ditto on the clothing. We long ago went to a parallel setup in our household. The only clothes that go back to Mom's house is the clothing on their back. She has her set and we have ours. Alex has a video discussing this issue. He filed a motion for that in his case and he got a judgment ordering his Ex not to steal the clothes. This won't help the situation that the Dad doesn't provide clothing in his own household. But it will keep you from losing clothes. You can document that he is not providing for them at this point. That could come in handy later.
Explain to your Ex that you will sit down with the kids and inform them as to what is appropriate behavior by an adult anytime this happens. Don't denigrate your Ex to the kids. The courts don't like that and that can come back to bite you later. But you can tell your kids the difference between right and wrong. Some misbehaving parents respond to a threat of a lecture of this sort. And along with this idea send him something in writing every single time it happens. You can keep it brief but make sure it is in writing. The first 3 letters like this will just get ignored but his 'Spidey' senses will go off when he gets the 4th or 5th email. He may start worrying you are building a case and you should see that behavior improve. That happened to us - we saw the bad behavior improved after a couple of months of just simply pointing it out to her in writing. Read up on how to send BIFF emails - Brief, Informative, Friendly, Firm.
So you get the idea. Those are trite examples based on what you wrote. I'm sure your years of experience with the situation will produce better ideas for boundaries. Just make sure you state the inappropriate behavior and have a consequence that doesn't involve infringing upon his person or his rights. That's the best you can do without legal recourse.
Hang in there! The fight is worth it for those kids.