With 220V you are playing with fire and you need to exercise extreme caution. If you are deriving 220V from the mains, you will probably end up getting 340V dc by the time you have rectified it.
It is possible to run such a circuit with 220V dc, but you need to know what you are doing.
Rate the FETs to 400V minimum to allow headroom for breakdown etc
You can use a 1N4007 for D3
R6 and R7 are explained above - they stop oscillations
When the outputs Lo and HO go low, D4 and D5 provide a fast discharge of the gates of the FETs (they bypass the resistors R6 and R7). 1N4001 should be OK
Your circuit should be OK providing 6A load current without a transformer
I still have grave reservations about using this circuit with 220V, but it should be possible if you know what you are doing