Unfortunately the case is that we quoted for two hours work when starting this upgrade, and I do not believe that the problems are necessarily our fault. There is a HUGE amount of incompatibility between xenforo plugins, and many people have add all of these problems when upgrading, some have lost their site simply upgrading one plug-in. We are now in a situation where we are fixing problems with the xenforo code. The blog upgrade has a lot of bugs that can make the whole site inactive.
I know you don't see why upgrading the forum should affect the layout on mobile devices, but the fact is that we are unable to upgrade the mobile layout plug-in, so we have to assume that it is now incompatible.