You cannot see a mob's actual hitpoints (we don't and have never had that data, we just get %'s).
There are various custom UIs that have autoattack timers but the default does not have that built in by design unfortunately.
As for using individual pieces of Fetish -- it can be done but the pieces aren't packaged individually. You'll either have to extract just the specific files you want (which must include all of the supporting stuff like the styles, etc.) or extract everything and then delete the files for windows you want to use the default for; when the game looks for a needed file but cannot find it in the custom UI directory it will automatically use the default version of the window.
__________________
|