Congratulations on coming out of your treatments in such good shape. May your good fortune continue.

You have been getting good advice. Rehashing a few things:

Adjust your eating habits so you'll drop the extra pounds.

Keep riding with the faster group. Keeping up with them will make you faster when you ride solo.

Adjust your gearing to match your riding. I think smaller big and middle rings combined with a narrower range cassette would serve you much better. Leave the granny ring for extreme climbs, but use the other two to cover the range you need most often.

Take it easy once in a while if you can do that without causing yourself too much stress.