You may want to blend it with something else, that really works well.

I doubt you can pull much more than 1g/l out cold stabilizing. If the
pH was at 3.2 or lower you could try calcium or potassium carbonate but
3.35 is not bad. Maybe do both, some potassium carbonate to reduce it
1g/l and then cold stabilize. A little sugar goes a long way on tart
wine too.

Don't do anything until you get good chemicals. A tart wine will keep
practically forever, you could have worse problems...

Joe