1. Yes.
2. Yes.
3. Yes.
With the air strike on a unit in a building, there is nothing suggesting you do anything other than roll for type of aircraft as normal.
That being the case, depending on the roll you could have:
2D6 hits, +2 pen, no HE special rules such as ignoring extra protection;
1 hit with 3″ HE (2D6 hits, +3 pen, HE special rules) or;
1 hit with 4″ HE (3D6 hits, +4 pen, HE special rules).
