I haven't had such a massive negative reaction to a website for ages. The design is irredeemable - some sort of bad imitation of this one (which isn't great either), then on mobile it stays bad but with completely different colours. There are blank spaces everywhere. Go back to Vanilla forums and get one of their tried and tested themes and start again. Ultimately it's a forum and forums have had their day. Those that hang on, like this one, are shadows of their former selves.
The lack of padding on many elements -- including the header -- feels like rendering errors, pretty much every combination of white and mint green is below accessibility mimimums rendering text illegible, which is doubled down on with the absurdly undersized fixed metric (pixel) font and element declarations telling large font / non-standard default font size users -- like myself -- to f*** off. It's such a complete /FAIL/ at basic accessibility minimums, I'd be shocked if anyone bothered to use it.
What's with the 23 js files and 11 stylesheets and MASSIVE raw js in the head? I have viewed a lot of source files over the years and have NEVER seen one built with dozens (maybe HUNDREDS) of SPANs and almost no DIVs. Most sites never use SPANs but use hundreds of DIVs for nothing. I don't see how you are going to fix any of the issues @deathshadow has noted. In fact, I don't think anyone (or any browser) can understand your code.