Where is the option to rebind the key to end turns ? are we stuck with enter ? 

I went looking for this also, i like to put one of my extra mouse button as a 2dnary binding for that so it's easy to stick to all-mouse if i'm in that mode.

i usually use space for that, so i did a script on ahk

Space::SendInput {enter}

just replace space with any other input you want to use