Ok it seems one of your 3rd party plugin is causing the issues. I’ve deactivated “Head, Footer and Post Injections” plugin & it’s loading the donation page perfectly. Also one thing I would like to inform you that please try to upgrade your server. PHP version is currently 5.4 which is too low & you should upgrade to the latest version which we recommend also. Another thing is that you should update the theme to latest version which has latest security patches & other things. Please avoid using untrusted 3rd party plugins usage.
Hope this would help you in cases.
Regards