1. 10 hours per day is probably OK -- but make it (2) 5 hour sessions, not 10 straight.

2. Once is fine.

3. CH isn't going to change unless you add calcium, begin using cal hypo, or add so much bicarb or soda ash that you cloud the pool. TA -- if you are going to keep the pH low enough to strip carbonate alkalinity, you probably want to test more than 1x per week.