For the last part. It doesn't matter, no dynamic campaign in DCS :)
When I did this mission I just took off from the parking and made CDU alignment in flight while looking for the mortar (well hidden :O )
Gun sight is not really important for mortar, it's better to make a pure strafe run with dispersion to get all of them in one or two pass.
I got aligned enough though for the next part of the mission to get an pretty accurate gun sight :)
Adjust your trim one and for all when in pre-contact, flying formation with the tanker.
Then don't touch it anymore, just push a bit on the stick at each acceleration and vice versa :)
I think in the last version of the mission, it's not anymore on the FM VHF (that does not work) but on the UHF radio for homing.
I tried it but didnot hear nything on the provided frequency and the given coordinate (damn lat/lon coordinate) are quite accurate enough :)
Basically it's another word for a door lock or a lock.
Without it you have to keep pressing the button, with it one push is on, one push is off.
edit : totally burned with the new page ;)
ADF related mission now...
It's nearly the end :(
edit : by the way, in minebuster, GBU-31 is a huuuuge an really heavy bomb, getting secondary targets before releasing them was a bit fun after my first gun pass when I pulled up :O
There are blue infantry next to the practice target red tanks.
Just send a flare rocket to one of the thanks and call the F16's and voila, mission over :)