I don't intend to sound rude. Nor do I wish to interupt anything that anyone else here is trying to do to help.
I live up in the Conroe area and if it'll help, I might can get out to look at your horse this week end. I'm not an expert by no means but I do have a vet that comes by my place when I need him AND I am in a position to give daily care to an ailing horse.
The only hitches in the glitch might be......
I currently have two (healthy)horses myself which get along just great. I can't however, say ahead of time how well my mare will accept another. But I'd be willing to try, if it'll save your horse from being put down.
The other thing is.... I'll want to talk this over with my vet before I commit to assuming ownership of a sick horse which will be pastured with my other two.
If this sounds like it might help you at all, just reply here to let me know and we'll go from there.
Hope this helps and good luck to ya.