I'm not part of the BP staff, but I think I can answer your first question. The Sol gate is based off Knossos technology, which just stabilizes a natural jump node; any ship capable of using a jump node can use a Knossos or the Sol gate. (This is in contrast to the UEF intrasystem gates, by the way, which are basically intrasystem jump drives in reverse.) The only relevant command codes were the ones the NTC Trinity used to activate the dang thing in the first place (which, hm, could make for a cool campaign premise, but I digress). Remember also that shutting down a Knossos doesn't immediately do anything, or FS2 would have ended at A Flaming Sword, so the Alliance doesn't have the luxury of toggling the gate to control access.
The gate does, however, mount beam cannons.
Strictly speaking, canon doesn't rule out the possibly of jumping in or out right next to a jump node, but since that makes nonsense of so many missions, it's widely assumed to be impossible.