Bill, you are correct in that yours would be 20% (plus tax) of what your current license would cost now. I know any code changes would cost extra but you would have to look at the description of the upgrade at this URL
https://clients.phpfox.com/cart.php?gid=addons or Product Addons in your PhpFox client login. Mine says the following which I question about it not saying the free chat stuff in the description but they provided the link so it must be right. Here is the description for V4 Pro
phpFox Annual Upgrade - V4 Pro
This addon is for the annual update plan for phpFox V4 Pro license. The access to new phpFox versions will be kept in next 12 months.
So check your description for the Annual Upgrade for Ultimate so at least you will know. I have too many hacks to actually use V5 but I wanted it so I could at least try to help the forum if needed. I understand your frustration though...sorry. Winter is coming so I will be back inside in about a month if you still need help.
Yes, phpFox uses Video.js to play videos on the site, however, it doesn't support ads currently. So sorry for this inconvenience. However, our development team is going to consider having necessary improvements for Video in future upgrades.
For your issue, please submit a ticket at https://clients.phpfox.com/ along with your site credentials, then our support team will get in touch with you shortly.