Help setting up my configuration properly

Ok, here is the scenario:

I've been running Bind 9 for some time now with one domain (call it mydomain.com) on one IP address (call it 1.2.3.4). I virtual host several domains on this IP address.

For some time I've been getting complaints that people are having problems reaching the websites on my server. I've looked high and low and haven't found a solution yet, but I have some ideas:

a) I don't have a reverse zone setup for 4.3.2.1, do I need to do this with a PTR to my server?

b) I don't have NS records in any of my domains, are these required?

Furthermore, I've added another interface with a seperate IP (on a different subnet) and I've also purchased another domain, call it mydomain2.com on another IP address (call it 2.3.4.5). What I'd like to do is setup this as my primary nameserver, ns.mydomain2.com and then my previous IP and domain as the "slave" at ns.mydomain.com. Even though they will reside on the same physical box, it sets up for future expansion and allows me to transition web sites with no downtime while I begin eliminating mydomain.com. I'm quite unsure how to accomplish this on one box, can anyone assist me with an example configuration I would use or at least a point in the right direction?

Thanks in advance!