WSGIPythonHome will not do anything because you are also loading mod_python into your Apache instance. In that case, mod_python overrides what Python version is being used.
This is mentioned in the documentation for WSGIPythonHome.
Also read:
- http://code.google.com/p/modwsgi/wiki/InstallationIssues#Using_ModPython_and_ModWsgi
- http://code.google.com/p/modwsgi/wiki/InstallationIssues#Python_Version_Mismatch
- http://code.google.com/p/modwsgi/wiki/InstallationIssues#Incompatible_ModPython_Versions
Also, WSGIPythonHome is not meant to be set to the path for the Python executable anyway. So that would have been completely ignored even if you had only been using just mod_wsgi.
So, if you don't need mod_python, stop loading it into Apache.