You can follow this help guide in changing the default support email address. In regards to your second query being prompted for a host, URL, and Token, this pop-up would only appear on a couple of scenarios during enrollment. 1 the downloaded installation package is already expired (EM Portal> User list>select the user. user tokens tab). 2 the file has been modified (renamed etc ).
As of the moment, Our Product has this feature enlisted as work in progress to disable the submit ticket option. Our current workaround is to hide the communication agent icon which is a setting that can be controlled from Profile>UI Settings [show communication client tray icon]. Unmarking this option hides the icon, thus removing the option to click it.