1)
Why did he flee via the window?
1.
Radak: He could not leave via the door, due to the guards. His house had a window on the other side that the guards did not see.
2.
Radak citing R. Eibo, Shochar Tov 59:4: There were two gates to David's house; one was locked. They guarded this gate, and he fled via the other. 1
3.
Radak citing Rabanan, Shochar Tov 59:4: There was one gate to David's house. They guarded it; Michal lowered David through the window, and he fled.
1
The verse explicitly says that she lowered David through the window! Perhaps he holds that even after this, he needed to leave through a gate, and explains why they did not guard it. However, what forces him to say so?! (PF)
