1: if the war happens it will deal dmg as defender, although I don't know if the war will even begin in the first place. Never seen situation like this, nor tested it.
2: The enemy should not even see your subs in this instance, so you should pass safely
3: probably depending on refresh of the server, so it's basically random, but as with the #1 i never tested nor seen situation like this myself, so not sure.
For tips i can only tell you, that agressive mode is good idea only if 1: you are guarding your border with arty and it has no enemy units in range, but you expect an enemy attack, but have to go offline. If the attack happens, your arty wont be waiting for enemy to run into it, but will fire imidiately as the agressor comes in it's range. Personally i also used it to conquer bots in lategame, as i was the last man standing and needed VP, had a lot of arty, and was too bored to personally guide my units, so i just sent arty on aggro through all provinces on map and logged off, just to see them in two days cleared the way and conquered what i wanted them to do, with few provinces left behind as revolted
