Can a mortar fire at a hex with nothing in it? Just to put the FFE down to either help with moving up behind the degrading hex of the FFE or try and keep someone from moving into that hex?
"Mortars can also fire indirectly at spotted hexes to which a Leader/Scout has a LOS. Leaders/Scouts can call onboard Mortar fire against a hex they spotted during the current impulse." - rulebook page 48.
As long as the leader has LOS to the hex he can call in mortars or OBA. So yes.
If you are IN a bunker and get hit with a Flamethrower and are shaken. Do you JUST get out of the bunker and stay in the hex or do you get out of the bunker AND back up to another hex?
"Units inside the Bunker are considered to be in a separate hex from the hex it is in. A Bunker is like a hex within a hex." - rulebook page 57.
"The retreat must increase the distance between the retreating unit and the unit conducting the Flamethrower attack. The retreat cannot reduce the distance between the retreating unit and any other enemy unit in the retreating unit’s LOS." - rulebook page 8.
Taking those two notes into consideration, i'll go with a "ELIMINATED" result for the poor shaken units.
I mean, they are shakened by the fire, they move away one hex ( that will be the same hex they were in since the bunker is considered a hex within a hex ) they will find themselves at the same distance from the attacking unit not distant as page 8 says so they are eliminated.
Probably the fire was also coming from the outside and they all perished.
Leaders can NOT user their LD modifier when spotting.
Leaders CAN use their LD modifier when spotting.
"Leadership Modifiers apply and are subtracted from the die-roll." - rulebook page 25.
If you LC you can move one hex no matter what the movement cost unless prohibited(like by three hill slopes) but if it was a legal move and cost 8 MF you could LC.
"units with a MF equal to or greater than one can always move one hex, no matter the cost, or enter/exit a Bunker or Cave or change one level of a Multi-story Building within the hex they currently occupy. If a unit must expend ALL of its MPs to move one hex (or within one hex) it cannot Low Crawl or Assault Move into the new hex." - rulebook page 18.
Pretty clear they can move into the 8 MF hex but not low crawl into it.
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And that's all! I hope i've helped! Pretty tricky questions i must say
Also i hope you don't mind if i used direct citations from the rulebook as it will help other players to know from where i gave you the answers.
See you!