Second post after several months trying forum's advice. Feedback please?

So my first post was here:
http://www.poolforum.com/pf2/showthr...Test-Treatment

I have followed a lot of the advice of everyone in the forum & my pool has looked fantastic throughout the winter. Of course now comes my first experience with spring. And spring in Texas is probably a little more like everyone else's summer.

Anyway, here are my values as of a complete K-2006 test this morning:
FC = 0.5 ppm
pH = 7.8
TA = 90 ppm
CH = 375 ppm
CYA = 110 ppm

A few notes & questions to tack onto this:
1) I have already taken action on the FC content. I added 64 oz of concentrated bleach (8.25%), which works out to just about 6 ppm in my 10,000 gal pool. Will test again in 2 days when back from the weekend.
2) My pH has been swinging wildly between 8.0+ - at which point I usually added 1 qt of muriatic acid per Taylor's guide - down to 7.2. The pool tends towards a much higher pH constantly. If I'm at 7.2 or 7.4, I can expect 7.6 within 2 days, and 8.0 within the week easily. This is with or without adding any chemicals. What gives?
3) I dropped 2 lbs of baking soda in about a week ago because my TA was about 110 ppm or so. It had its desired effect, but also looks like I now need to add more muriatic to bring pH back down. Correct?
4) My FC has been depleting at a pretty rapid rate each week, even w/ highs in the 40s and very little sunlight. With such a high CYA content, I would expect the opposite. What the heck is going on?
5) I saw the CYA correction to TA in the back of the Taylor guidebook. Does this calculation have some effect on what I'm doing here, and do I need to adjust anything accordingly?

Thanks everyone.

Sorry it's taken so long. Everybody's been a bit out it for the winter. My pool's been frozen for a couple of months now (that's good..makes spring opening easier).
First things first.
1) Your FC is 'way too low. With a too-high CYA of 110, you need to keep your FC at 8-15 ppm routinely, unless you have an SWG. If you do, the numbers are different. If you need to shock raise it to 25ppm. They are too low. Otherwise consider draining half your water and refilling to get CYA down to 55 or 60ppm--much easier to maintain. Check the "Best Guess" table on one of the threads or at our sister site Poolsolutions.com.
2) pH can vary widely. The 2006 should have reagent 0014 with neutralizes chlorine...high chlorine makes pH appear higher than it actually is. Generally, with a vinyl liner, 7.2-7.4 is a good for spring cleanup as chlorine is more effective at lower pH but pH isn't low enough to damage your liner. Also, if you have things like fountains and water falls, they raise pH (aeration of water drives pH up).
3) since the recommended T/A range is normally 80-125ppm, why would you add baking soda to increase it when it's 110ppm????? Frequently, when people have the pH constantly rising we have them LOWER T/A to 60-80ppm and that helps. Please see our ways to LOWER T/A. Get it down to 80ppm for starters and see if that reduces your acid demand.
4) See #1. You have (probably) algae and with your high CYA levels you're not getting enough chlorine in to fight it and it keeps depleting the FC and growing again. This is an extremely common problem. You must raise FC to 25 and keep at that level, checking and adjusting 2 to 3 times a day till FC stops dropping for 24 and your algae is dead. Then you can slowly let FC drop (it will) and maintain at the 8-15ppm level.
5) No.
Let us know.
Carl