It may be better to take him to a vet. Attempting to reset his legs by putting braces on them may cause him a great amount of pain and not do any good. And please don't think about breaking the bones to reset them!!
The vet may be able to correct the legs. I would suggest if the legs and feet are really deformed its a lot simpler to remove the feet. This sounds drastic, but I have a rescued feral pigeon which has no feet.. only 2 leg stumps. It gets about fine and is really happy. Only thing I had to do for it was to give it wide flat perches, as it could not grip round ones.
Keeping my fingers crossed for you and you little friend.
I have about 15 rescued feral birds, some with one leg, one eye, missing feet, crossed beaks, partially missing wings, etc. They are really hardy tough creatures that don't let their disabilities get them depressed... so don't let the vet tell you its best to put the bird to sleep... they always seem to like to suggest this for all wild birds. But if you are willing to care for it for life, then it can have a happy life with you.
Please let us know how it goes.