I just have to say, I almost teared up seeing those photos and not a lot bothers me. You are a true angel, of the purest spirit, to do such an incredibly kind deed for this little pony. Although euthanasia is probably best, I am sure living out his days in your paddocks will still be 10x better then the life that awaited him until his eventual death probably sooner than later.
I agree with others, I would attempt to locate the best "farrier" you can, or even try it yourself. As terrible as it sounds, it doesn't seem like there's a lot you could do to make him worse if you're careful. If you've done your own hooves before, you know the basic do's and don't. It's probably better than being left, or being touched by someone who doesn't know/care.
Just a word of warning, we have a club footed Miniature and an idiot farrier who claimed she catered to all horses feet and then trimmed every one of ours like halter Quarter Horses actually made him bleed. She tried to cut into the foot the same as a normal foot, but obviously due to the natural excess length and structure it doesn't work that way. However, she went HARD on the foot and didn't even play with it, she'd obviously never dealt with club foot before.
Another reason why it may be best to do some research and try it yourself. Give yourself plenty of time and go as slow as you can!