OP, please be extremely careful with lowering the heel of the club foot. If it keeps growing back quickly, it's trying to tell you something. Something higher up in the leg or even shoulder is off and not able to function effectively yet. When you see the sole near the back of the foot shedding, it's ready.
I'm a few months ahead of you in terms of working with a club/flat foot horse. What worked for me is to forget about the club foot. As eager as I was to get the heel down on my horse's club foot to get the boney column aligned, the key to the club foot was the other foot. Like your horse, it was flat, with a long toe, and under run heel. When we first pulled the shoes, that flat foot went splat. First thiing I did was put a padded boot on it. The rest was addressed entirely through trimming. Every time that toe tried to creep forward, we knocked it back. At the same time we played a tight rope game with the heel. We kept dragging that back the moment it started growing to keep it from growing forward, but not so short that he had no heel. Any excess hoof wall was kept beveled to the 1/16 above the sole to prevent laminae separation which would have made the flat foot flatter. About two months in, I suddenly saw the sole on the club foot shedding, so we took a smidge of heel off. Two weeks later it shed again, we smidged again. About a month ago, the flat foot unflattened, grew some heel, the wall thickened considerably and it began to support itself. The overall shape has become so much tighter and less flared that I had to go down a boot size. The two feet have now settled to where they will probably remain long time.
Sorry I wrote a book, but my point is, be patient and let the club foot tell you when it's ready to come down. I really belive the key is in the flat foot. My horse now grazes with both feet even or interchangeably. He's still a long way from a barefoot horse, but the trimming has definitely been the key to date. Keep your toes short, don't allow excess wall, drag that heel back and you'll get there.
You just have to see your distance...you don't have to like it.