Evolution -----> Mozilla
 

Does anyone know the command to force Evolution to use Mozilla as its browser for url clicks?

you have to set it in gnome control center.
run # gnome-default-applications-properties in a terminal.

And is there any setting that wud make evolution open different url's in the same mozilla window using different tabs?

if you're running evolution 1.4, have a look at http://lists.ximian.com/archives/pub...er/011435.html.
f you're running an older release, look at http://lists.ximian.com/archives/pub...er/032489.html
I hope it'll help.