Use of Executive Order in Battlestar Galatica
Much of this is covered in the FAQ and Errata, which you can find a link to here.


You can't play 2 Executive Orders on the same turn.  Under Errata:


  The “Executive Order” Skill Card should include the following
  text: Limit of 1 “Executive Order” card may be used per turn.

Revealed Cylons can't play Executive Orders on each other (though un-revealed Cylons, sure!). Under Cylon Players:


  Q: Can a revealed Cylon player be targeted by the “Executive
  Order” Skill Card or Quorum Cards?A: No.

Yes. Under The Brig and Sickbay:


  Q: Can a player in “Sickbay” move out of that location if
  targeted by an “Executive Order” Skill Card?A: Yes. If the player moves out of “Sickbay” before the start of
  his turn, then he will not be restricted to drawing a single card.

I read it that a player may not move out of the Brig voluntarily, not even due to an Executive Orders free move. I don't think anything explicitly states this rule, but I generally feel that "You may not move" from the Brig trumps the "You may move" from Executive Orders.


As for your house rules, the first rule is good (and in the Errata).  The second rule seems to be not strictly in the rules, and I personally don't think it's a good idea - it would make Executive Orders more powerful than it already is (which is already quite powerful!) and the Brig less bad.  The Brig is supposed a scary place to be and hard to get out of; being able to Executive Order someone out of it seems like it diminishes that too much for my tastes.