"Files and folders permissions - please click here to find out if permissions are correct. (Opens blank page)". 

Permissions check opens up a blank page for me too. I don't know why.

Can you raise the php memory limit in php.ini?

disable_functions is also in php.ini. When I tried a cloud server, they automatically disabled the functions and I couldn't change it in php.ini. I had to switch servers. Are you on a VPS or cloud server?