Try clearing the top 2 mouse bindings then bind mouse axes to pitch and roll. That way you can directly control the aircraft instead of controlling the "go here" cursor.
The missiles are reliable in their kill envelope, which admittedly seems quite limited. STDM seem to have great success when the target is stays within a 30-ish degree cone from the launch position. To hit, you pretty much have to be either head-on or in a tail chase.