Never edit a vhost file manually. Manual editing will just mess up the setup and all manual changes will get removed automatically anyway. Thats why it does not matter much for the user where the fiel gets stored as he should not edit it.
To your original problem, set redirect in the website options to "No redirect" and do the same in alias / subdomain options if you added any. Then wait a few minutes and try again.
Regarding the redirection, you can use this only if the cms or wiki that you installed does not use any .htaccess files. Otherwise the redirect rules from ispconfig maight interfere with the .htaccess file and will cause redirect problems.
In generella it is not recommended to use a different root dierctory if the website cinatins any active scripts like php. If you need a separate directory for a subdomain, then create a new website for that subdomain.