I think that the move or shoot restriction of Heavy Weapons only applies to the appropriate player turn, since otherwise heavy weapons can never shoot if they've moved once in the game "If an Infantry unit moves then it cannot shoot heavy weapons..." (
BGB,
pg.29) If somebody moves their las/
plas squad, that's it. No more shooting for the rest of the game!

In response to your second question, "Remember that vehicles cannot move over friendly models..." (
BGB, pg70) and "Skimmers can always choose to move over
enemy troops..." You can't drive your Devilfish over your own Fire Warriors, which should take care of that one!

*ahem*
I've always thought that skimmers should have a "ground-hugging" mode for Tank Shock, much like how Jump Packers assault only on foot. By turning them into ground vehicles for the duration of the Tank Shock, skimmers would have to take dangerous terrain rolls for driving them into terrain, which seems a bit more realistic then just flying 50 feet overhead and scaring people away. *shrug*
The Fire Warriors will probably have to displace much in the same way as the enemy Tank Shocked unit. In any case, I don't see any reason why the
FW squad couldn't get back onboard their Devilfish or alternately shoot.
edit: Beaten! Nuts!