I would also go more
I would also go more conservative on the ramp up…especially since it sounds like a lot of work has gone into it. Was this your original firing schedule with the layers?
Also, instead of using coarse or other frit, small chunks of glass that you make yourself may produce clearer results, if you can fit them in there. Maybe even small bits of clear stringer. Coarse frit, even when washed to remove the dust, can produce tiny bubbles.
Another thing I do…if I have bubbles that are bothering me, is to turn the piece upside down, and fire a little hotter to force the bubbles to the middle of the piece and make them part of the design!