"Is there a maximum amount of wikiplugins in a wikipage? Or a maximum plugin inside plugin inside plugin? "
There is no pre-determined limit so it's according to server resources. Are you using XCache or APC? If not, I suggest you try.
Also, maybe try PluginInclude to split your content in several pages?
Also, it's not so much the quantity but it could be that certain plugins or syntaxes are making the system choke. So trial and error of different parts of the page can maybe reveal some hints.
If you can reproduce on demo.tiki.org, community developers can take a look.