Lurked on this thread since the beginning.
OP, I feel for you but I think you have to stop caring about this stuff as much. Easier said than done, I know. But it sounds like you have a great DP now, your girls are well on their way to becoming lovely young women, they are happy and well-adjusted, your life may be tough at times but you've got it under control and you're staying on top of all that it involves -- working, raising kids, being civil to your EXH, etc.
So ultimately look at the long run and the big picture and admit to yourself all these arrangements are only for another handful of years at most. And your girls will realise over time if they haven't started to already who cares for them and who doesn't. If their dad treats them like handy female skivvies, they will see right through that without your help. The church thing, the fact that he doesn't do anything with them, doesn't actively parent them or care about what they do will not go missed by them in the long run.
In terms of the things that are safety issues, by all means address that. But be prepared for the response. If you say "the kids can't be alone mucking out stalls in he morning, it's too dangerous" and he says "well I'm not getting up to supervise them, so the ponies will have to go" then your options are either letting the ponies go, or getting out there yourself in the mornings to do it. So you either call his bluff or do the extra work yourself. If you're not ready to do either of those two things, then you have no leg to stand on here. He controls where the ponies live, he controls their care and by extension, he controls you.
For the rest of the stuff, as annoying and frustrating as it is, I think you just have to take the high ground and stop caring about him as best you can. Stop letting him get to you. Stop letting his behaviour direct yours (e.g., no more of this DP can't go to events in case EXH is there - that all ends, he does not deserve you to care about his feelings anymore!) The guy is just a jerk and unfortunately while your kids are still young, you're just going to have to deal with that. But you don't need to let him control you, you don't need to care what he thinks of you, you can laugh him off, rise above it.
I've said this several times on MN but "the person who cares the least about a situation controls it". You are getting screwed over by your EXH because he puts you in a position where you care more than he does about whatever's happening. So his turning up late - you care more, you get annoyed, he controls it. But if you stop caring more and just do your thing, suddenly he might start caring and then it the tables will turn. He will not like being manipulated like this, but currently he's manipulating you so I don't see an issue with turning it back on him 
. 50/50 is his big thing, right? Start seeding the doubt in his mind that his 50/50 is a joke and watch how fast he starts to take it more seriously.
To do this effectively, you need to reduce how much you depend on him, and how many opportunities he has to control you. Probably not completely possible, but at least you can try, and in the situations where you have no choice, just accept it and let it go when he screws you over.
Hope this helps, half the battle is changing your own attitude towards him and freeing yourself. Yes, it's hard work and yes you're in for a few more long years with this idiot, but in the long run you will be happier. Good luck.