Here is a little tidbit to help you deal with your new body after losing so much weight. I went from 220lbs. post ACL reconstruction to 175lbs.ll
Since you are having trouble with catching edges, it sounds like you are reluctant to actually put your board onto an edge while you are progressing down the hill or across it. I'm sure your muscles aren't used to the new pressures you are exerting and you just aren't using the right muscles.
I'm no instructor, but after a long time away from my board, I usually put the boots on, then strap into my bindings and board in my bedroom with my bed behind me in case I fall backwards, and start to do some squats with weights and practice putting the board on each edge while in a pretty athletic stance. This is just a suggestion, but it should help you get used to using the muscles a bit more than you are used to. Try doing this for ten minutes a day for a few days the first week, then 20 minutes a day and so on.