In my time there were always one or two guys with a reputation for unnecessary aggression. They were not respected for it, but were viewed with a mixture of caution and contempt. So I'd work to avoid being that guy, were I you. Granted, there were/are other guys -- Paul Swift and Gibby Hatton always come to my mind -- who had the reputation of being able to deal with anything they needed to. They didn't earn it by being ******bags so much as by how they responded to ******bags. For whatever that's worth.
As for the paceline question, first a clarification: I assume that by "paceline", you mean a situation where the pack is strung out in single file while going fast. If you mean guys rolling around at moderate speed and trading pulls in a race, that's kind of out of my experience, because I hardly ever saw it. In my time, the group was bunched up while going slow or medium, and strung out while going fast. if that's changed then I dunno what to tell you.
So in that context, when a jam starts everyone is looking for a wheel. If you get caught out, the problem is not so much how to get a wheel, but how you ended up not getting one in the first place. If you keep your eyes open and your head up, you will see the jam developing and you will be able to jump early enough to get yourself a spot. In fact, if you react quickly enough you'll find yourself at the front, from where it is perfectly acceptable to simply stay in the pole and slow down, forcing other riders to pass you. When you're where you want to be, accelerate onto the wheel you want. The only real problem is if the jam is as a result of an attack: you going slow at the front is going to hamper the initial organization of the chase. Unless the guy off the front is your teammate, this might not be in your best interest.
If it's too late, and you find yourself in damage control mode, then your best bet is first to get onto someone's hip. If you crowd right down onto him, the guy behind will often just drift back to let you in, again if it's not an especially valuable spot. And if he doesn't, then you can slide back a bit more aggressively, to "encourage" the fellow to give up his spot. There is some risk to this, primarily from the owner of the hip you've been riding: if he makes a sudden move, you're vulnerable. Beyond that, don't really force the issue. If the fellow you're trying to drift into is stubborn and really wants the spot, it's his, legally and "morally". Either drift back another spot and try the guy behind him, or stick tight to the hip you're on and hope the jam ends soon.