XF 2.2 Question about permissions


I would like to have the following setup:

1. Free members can post quote requests inside a particular forum. (Already fixed this)
2. Premium members are the only ones who can make offers. Everyone should be able to see them though. (This is just normal permissions right)
3. The free members can then reply to their quote request inside that particular thread. (Is this possible to give free members, only the possibility to create threads inside this particular forum and give them only the ability to reply to their own threads?
4. Once the deal is sealed they must change the thread prefix to Deal Sealed. (Already fixed this)
5. I will set the pm (conversations it's called here I guess) to not possible for free members, can I give them only the opportunity to discuss the deal with the supplier who won the deal?

I hope you understand what I mean and I hope you can help me out. If there is a better way to do it then I'm open for suggestions too.

Thanks a bunch!