Warren,
It sounds like you are doing very well under the circumstances. It also sounds like you are really pushing yourself. Nearing the end of radiation I began to feel tired and although I would buzz into the office for a little while and check mail, etc., I certainly did not work too hard or try to accomplish too much. Unfortunately I began to feel really worse and hit my lowest spot just after radiation treatments ended. I don't mean to pass on depressing news, but most of us had the same experience of feeling our worst in the first couple of weeks after treatments ended. The good news is that, in time, this passes as well.
I just finished playing in a three day golf tournament in the hot Texas sun with temperatures in the 90's...and did pretty well. So, there might be some bad days, but you have a lot to look forward to. Best of luck with your recovery.

Regards,
Danny G.