I hope I'm being as clear about this as I can...so hear goes. This might be long.

Something is up with my TA...I think. Last Thursday, I got my water tested at the pool store, and I tested it myself with Wal-Mart Kit.

My #'s (Pool store #'s)
TC=3-5ppm (FC=4ppm)
pH=~7.8 (8.0)
TA=300ppm+ (120ppm)
Hardness=0ppm (185ppm) (i'm going to ask about this in another post )
CYA= less than 20ppm (0ppm)

So, that evening my husband added fill water, 4lbs of CYA, 1 trichlor puck, then 1/3-1/2 gallon of muriatic acid. Friday morning, TC was still 3-5ppm, pH was ~7.6, TA was 230ppm. (went swimming )

Saturday morning TC 3-5ppm, pH=~7.8. We were going away for the weekend, so I added 1 gal of 10% sodium hypo to bring TC up to ~12ppm and 2cups of acid.

Sunday evening, got home and tested. TC=5ppm+, pH ~7.6-7.8, TA 190 ppm. It also rained on Sunday. I added 2 cups of acid.

My questions are:
1. why does my pH keep drifting up?
2. Should I trust my TA numbers? I know it's "normal" to have a discrepancy in pool store vs. home kit readings. It is going down, which is good. But from what I've been reading, it's normall really hard to decrease.
3. Is tomorrow too soon to test for CYA?

Pool info: 12,000gal IG exposed-aggregate surface

I hope someone can clear this up!