Only airbases attached to a Front Air Command/Army will fly ground support for combats by units for that front. I have experimented with having STAVKA/Long Range Air Command bases near STAVKA armies in hopes that they will fly ground support for their friends but haven't had success. I would like to get a definitive word on this, though.
Therefore, I generally assign fighter, tactical/dive bombers, and short-range level bomber units to Front aviation bases. They do ground bombing and airbase bombing as well as ground support. In fact, I make it a point to bomb Axis ground units every turn until my air units get to about 50% of miles flown even if they aren't having much effect - it pushes up fatigue levels on German fighters and on the ground units you are bombing. If you get the impression that German fighters are at high fatigue or running out of gas/ammo, go bomb their airfields.
The longer-range bombers go in airfields attached to the Long Range Air Command HQ. They all get set on night missions and do air resupply missions, night bombing of German airfields (if you haven't been able to bomb them during the day) and maybe a little strategic bombing if you get the chance. The Rostock factories are vulnerable.
Don't forget about staging bases. Use of a staging base can increase aircraft range by about 50%, and the miles from the home base to the staging base only count half against the total of miles flown. So you can put your bases farther to the rear, have empty staging bases about 5 hexes back from the front, and still get plenty of use out of the air force.
The SAD bases will disband in the spring of 1942. You should have resources over the winter to build replacement bases. Don't worry about it too much during the good weather turns of 1941; you have plenty of more important stuff to do with your AP's.
And remember that if you lose 800 planes and the Germans lose 200, this is a victory for you.