If a tidal locked terrestrial sized moon with 0 eccentricity, 0 incline, and was orbiting .01 AU away from a gas giant with 12 Jupiter masses (which would have approximately the same radius as Jupiter), how much of the sky would said gas giant take up if you stood at the center of the inward facing side? If this orbit is too close to be stable and/or makes the surface extremely volcanic (like Io) for a long time, I would appreciate any suggested orbit sizes that will fit these conditions, and then an answer based upon those conditions.
A gas giant with 12 Jupiter masses and 1 Jupiter diameter is fairly realistic, there are known exoplanets just like that.
From 1.5 million km, it will look huge in the sky. Its angular size would be about 5.5 degrees - 11 times bigger than full Moon, and more than 2 times bigger than Earth when seen from the Moon. (Angular Size Calculator)
At this distance, the satellite will be well outside its Roche limit (about 125000 km) and should be stable. (Roche limit formula)
With tidal lock and 0 eccentricity there is no worry about volcanism. Io is volcanic because its orbit is not a perfect circle, and this is what causing its tidal heating.