Alright, you’ve got to the point where he will kinda pick up his foot; he’s trying, anyway, and that is what counts. Keep at it and he will improve. If the going gets too slow for you, remember not to be impatient! Patience is the most necessary virtue in horse training, and if you know you don’t have it, maybe someone else should train for you.
If, after a few weeks, he is still trying and just can’t quite make it, try this. First, make sure your horse is standing squarely (the front legs in line) on a flat piece of ground. If it is hard to stand on three legs anyway, standing him on rolling or unstable ground isn’t going to help. Now try again. Instead of dropping his foot as soon as he picks it up, hold it for 3 seconds. If he starts to fall, though, get out of the way! You don’t want to be crushed. Hold it for a little longer and bring it a little higher every day.
If the problem is that he leans on you for support when you pick up his foot, pick it up, and as soon as you feel him start to lean on you, maintain your hold on the leg, and move away from his body so he no longer has contact with you. He will stumble, he may fall, so watch out! (please do this on a level piece of soft ground!) He will never do it again, though he may need the reminder of stumbling again, but he will not allow himself to fall ever again.