Quick start HUGE messup

We got this template in one of our sites and now we are stuck with it. We got it working and everything was fine, while in offline mode. We got fixes from the developing team for some of the plugins. On official release date everything gone wild. We placed the site online and opened cache to speed it to normal levels and there the problems begun.
The products "ask a question" function stopped working properly the add to cart stopped working, even the menu malfunctioned. We closed the cache and everything worked as it should but it takes 16sec for the site to LOAD!!!!!! In my entire career i have never seen anything like this before! And as far as google goes no one else! We are extremly frustrated with this case. We tried cache handlers to manage the situation but they only made things worse. GotCache almost destroyed everything. And once the cache starts building it grows over 2GB in size and keeps building!

Could you please give us a solution to this problem?

Site:
maxsports.gr

Hi

I'm afraid what broke the site were modifications and wrong choice of extentions. Please simply compare our demo in a validation tool.

Here is our site, with just a 4 errors http://validator.w3.org/check?uri=http% ... 2Fservices all errors strictly connected with a propper code of facebook apps, just not recognised by validator yet (it's still experimental).

Now look at Your site: http://validator.w3.org/check?uri=http% ... 2Fservices , there is 16 errors more which has not came with template as You can see while comparing. This means that Your site has not been built with properly.