Let's Talk
Sounds like you have a bit of a tricky situation going on with your theme. I've been working with wordpress for several years but am relatively new to freelancer, so if you need references don't hesitate to ask.
Most of what you are talking about can be handled by a child theme, but that depends on how things are set up. I've not really seen two themes being used unless it's a child theme situation. It really could be a matter of copying the files from the first theme and integrating them in theo the second, but until I can look at what's happening and what is being pulled from where, it would be hard to guess at the perfect solution.
I'd be happy to discuss your project further with you.
My term on hourly work is usually minimal deposit to get started and then payment on completion.
Best Regards,
Deb Illig