Did you hard refrsh? ctrl + shift + r on firefox and chrome I believe.
Hehe I talked to the developer months ago, would need a plugin to do this and I don't know how to make such things
Well, you can always try installing it fresh not upgrading. Upgrading means you'll have to revert a few settings to get things to work correctly.
We do have an upgrade service. We generally charge anywhere from $20 to $80 for the service, depending on the issues that are caused. Installing fresh is the best bet, and then manually moving changes over. Like I said, this is the nature of the style property system. If I change something in UI.X where you changed something (child style or not), XenForo doesn't have a way of alerting you of the difference like they do in templates. Nothing I can do about this but ensure that such a huge update won't happen again.