We're just users here; you'd have to ask (probably via a helpdesk ticket) about any sales questions or official inquiries to the owner.
From a complete use perspective:
1. You need current member area access to download updates; the member center is here
and the purchase page is here
2. It costs $59 to renew, and $139 to buy a new license.
3. I usually email email@example.com vs use the helpdesk.
4. I wouldn't; vBulletin and IPV are bloated, Fusion is EOL. The development team is UBBDev, though the powers that be 'round these parts is a completely separate entity. Is there a reason you don't just click the "License Options" link in the Member Area and then renew from there? Am I missing something?
5. Again, these are user to user forums, and are not a valid support resource for the owners of the UBB.threads product.
6. Your theme should work, all of my themes
where made ~7.2 and short of having to occasionally load the style editor and make updates (things get added) they work fine.