Hi, I am so sorry about your horse. A very traumatic experience for the both of you I am sure. My stallion when he was 3 cut his leg
in that same spot I believe. (Cant really see your pics of it well, may be my computer screen).
His to was down to the good meat as I call it. My vet did the same as yours but he never told me he wouldn't recover. We were relentless in cleaning it so it didn't get infected. He too very much hated his stall but if you turn him out He will for sure bust it open I think. (My opinion) Buckshot did recover but his hock on that side is always going to "bigger" than the other. I didn't take any pics of it but I sure wish I would have so you could have seen how huge it was. I was for sure it was going to burst several times. Now he is fine, we don't ride him, he is just a big baby so I can't say if he is lame when riding. I would guess he would go lame if he was rode alot. I know this doesn't help very much, I just wanted to let you know that I have been through it as well. Hang in there! You are doing a great job from what I can tell. Hope he recovers very soon! Praying for your boy!