1 - Yes, as soon as mandoheliroute finishes a route, the chopper is freed so you can use it for anything else.
Good because that is what I have been working with using Mandoheliroute for the same chopper twice in one fight plan
2 - The only way to do that would be to modify the current code, check when the chopper is starting the landing sequence via mando heliroute, and just then drop the cargo (vehicle) while mandoheliroute proceeds with the rest of the landing sequence.
So simple it is genius.
Regards
Kendo