Yes. A Campaign is required. No, it is not necessary to have any leads (or any lists for that matter) in said campaign. Set the "no hopper leads login" to "Y".
The options to force the agent into the selected ingroups are listed in the Vicidial Manager's Manual (which you have, of course?). Basically it is in the User definition, you don't "force a particular ingroup", rather you "remove the ability of the agent to select", which skips the select screen and auto-chooses the ones selected by the administrator.
Thanks for posting your specs by the way. Not a lot of users are polite like that. Very helpful.
Also of note: You are asking Support questions related to Vicidial. Not related to "GoAutoDial", which is the installer. There are a lot more people on the Support board that could be helpful for this sort of question (thus the name of the board). This board is more for questions directly related to the GoAutoDial installer (CentOS, screens added by Gardo that are part of the GoAutoDial system but NOT in Vicidial .. and that cool agent screen GoAuotDial has that Vicidial does not ...). Anything not related to those things is generally best handled in the Support Board for a larger audience (and likely response!).