After some work I can finally say that I have a working system, both with support forums and selling, auto updates, license keys, downloads and everything else. It all works great, which is good news!
I will from now on have much more freedom with making bundles, set sale and discount codes, changing prices and so on.
Make sure to check out the new Pricing page. It should have an appealing price for everyone interested in my premium themes, and for people who want to support my work.
Every new purchase will come with user registration and automatic access to the new Support Forums too. Neat eh?
Currently I’m thinking of how to best include existing customers from ThemeForest to the forums. That’s the next thing to tackle.
A special thanks to Aristath for all the help.