My questions are:
1. are these things going to be possible with monowall? (if not, is there something that will do it?)
2. what services will I need to enable on the box to do this?
3. Would traffic appear to come out of the individual IP addresses or the one on the monowall box?
Thanks in advance for any assistance you can offer.
Yes, but not easy.
Look at
http://doc.m0n0.ch/handbook/faq-ipalias.html