So I too have the problem that the screen goes dark whenever I try to leave the strategic map without sending troops away...a state that even keeps around if then saved and reload.
I tried the "workaround" with talking to a chained slave and do a "walk of shame" ..which does reset the screen...only to then go black whenever the strategic map is entered.
So I'm stuck with doing missions and Stella being away...or her being in the training building but unable to do missions.
Alas, thats not much of a problem, and hopefully solved out at some point. Maybe I start a new game+ with the orb of restauration to kill some time...as boring that would be with a lv.57 mainchar and 400.000K coins *cough*
And yes, fullscreen is alt+enter.
p.s. A geeky sidenote. I was bored one day and went scrolling through the "characters"-folder containing the sprites...Is it just me, or is there no sprite for the "Rebel" soldier (the ones standing guard in the MC's castle) only "minis" used on the strategic map?
So that means that every instance those sprites are shown is...part of the map?