screenshot captor has a feature made for exactly this purpose.
The "File Name QuickField" on main screen is where you are supposed to enter things like a custom name for a series of screnshots.
the quickfield can be added to the default template in any way you want, because its just a field in your template.
OR if you DONT have quickfield entry in your template, quickfield will be used INSTEAD of your template filename.
i know its a bit convoluted but it's especially set up to do the kind of stuff you are talking about.
as for date and time, see the Templates field you have lots of choices, including a comepletely custom date/time
%quickfield% - quick text field from main screen
%datetime% , %date% , %time% - local date/time
%customdate% - obeys custom date format
%num% - 3digit counter
%windowtitle%, %filename%, %nicename%, %fullfilename% ,
%description%, %fileversion% ,
%company% , %productname% , %versionstring%