Lee, You are not far off from my numbers on Central Valley juice from Regina. I did a little experiment this morning on pH that you might find interesting.
I have a blend of 12 gallons of Cab Sauv juice, 6 of Cab Franc juice and 5 gallons of Cab Sauv grapes, pressed after about 5 days of fermentation on the skins.
The SG is 0.996, it is still 'gassy'.
I checked the pH without removing the CO2, it was 3.65. After a few second boil, it dropped to 3.55. Not a huge change, but significant to me.
3 other blends of different juices did about the same thing, all read a little different but the change was about -0.10 pH units.Here is the initial and final pH and TA of a white (Riesling)from the Central Valley this year.
Initial Current (3 weeks) pH 3.17 3.10
T.A. 5.3 (corrected to 5.8 preferment), now 7.7.
Other reds did about the same. All went up at least 1 g/l. All taste a little tart and will go through a cold stabilization which should drop out some tartaric, so I'm pretty much not concerned here.
In other words, I'm not sure you have to add any acid, my Riesling TA went up almost 2 g/l. If I added anything, it would be tartaric if it were mine, it can be dropped out with cold stabilization.
Hope that helps. Regards, Joe