I'm not completely clear what you're asking, but you're running the forum through the Joomla wrapper component and not through the SJSB SMF / Joomla bridge component.
Anyhow, for your forum pages, I'd recommend removing the left column link menu, so your forum members can easily navigate your page. This seems to be the partial reason why your page appears as it does when viewed through the SJSB forum component. The other is conflicting CSS. I can give you my CSS modifications, since I use the same template, if you'd like, but my CSS is slightly different than the look you have.