These 2 articles are specific to house rabbits. They may help answer some of your questions.
http://www.celebratingrabbits.com/stories/pasteurella.html
http://www.rabbitnetwork.org/articles/past.shtml
I don’t have personal experience so my answer here are my opinions only from what I’ve learnt from reading and other owners.
I don’t even know how to really answer Qu 1. My heart wants to say “Heck no!” As I’m sure does yours!
2) Will the meds have to be continued forever?
Quite possibly but that’s not to say he’ll need them every single day. From my understanding, there are flare-ups where you’d have to treat for severel weeks and periods in between where the immune system has it under control but never fully eliminated.
3) How much should I be concerned about George? They are brothers from the same litter and are bonded and always together. Should George be on antibiotics as well?
He’s likely a carrier and possibly as long as Cinnabun has been given they are litter mates. If he’s asymptomatic, he shouldn’t need go on antibiotics. Immune boosting for booth couldn’t hurt.
4) Will he die from this? Will his life span be significantly shortened? Will I wake up one day and he will just be dead? Or will he be able to live somewhat normally and die around the same time as his brother in another 8-9 years (they are about 1)?
I don’t think there is a definitive answer here. The articles I linked above will probably address this better. It sounds as if the infection is contained to his upper respiratory system. Rhinitis? So getting on top of those flare-ups when they occur means there’s less likely to be complications. He’s in a good position to do well because you’re obviously looking to give him the optimum chance to help fight the infection.
5) Is there anything else I can do to help him? I mean other than the antibiotics, should I change anything else to help him?
Minimize stress (beneficial for all rabbits of course)
Keep their environment temp & humidity fairly consistent. About 18C (64-65F) and 50-70% humidity.
Higher temps or big fluctuations in temp will exacerbate his symptoms.
Natural immune support like echinacea might be beneficial.
When he gets nose gunk, try clear it out for him (use like a baby nasal aspirator) and even pop him in bathroom that’s all steamed up.
6) Should he still excersize normally? Or will this cause his lungs to not function as well if he gets excited and runs around?
I want to say yes here. Let him carry on as normal. When he’s feeling poorly, he’ll moderate his own activity I imagine. I think not letting him out to run about like normal (if that’s what he’s used to) would cause stress and stress can be a trigger.
7) If I ever decide to get another rabbit, is it a bad idea because it then exposes the new rabbit to pasteurella?
I don’t see why you couldnt bring a new bun home at some point. Best to quarantine a new rabbit regardless. You could keep it housed separately and just practiced good hygiene between handling your pair and any possible newbie.