Are you using tri-chlor tablets in your floater?
What did you shock it with?
I'm wondering about your test kit. Is it the 6-way HTH kit from WalMart or something else?
Have you tested your fill water with the same test kit, too? You know, to get a baseline.
Tri-chlor tabs are heavily acidic and should drop pH in a 1200 gallon pool rapidly. If not, something else it going on.
Also, don't worry about your T/A at this point. When you get your pH down in the mid 7's T/A will drop as well, and anything under 200 in a vinyl pool is probably OK, and under 180 is definitely OK.
Since it's only 1200 gallons, can you consider emptying and refilling your pool?