"Mar bedithach" would obviously be *Mar badathog* in more correct Sindarin, in light of Parma Eldalamberon #17 and the future verb *cawathon* revealed in Parma Eldalamberon #22.
I thought "A star shines in the hour of our meeting" was "Elen sila lumen ometielvo" and "May the sun shine on your path" was "Anar kaluva tielyanna" Am I wrong?
There isn't actually a word for "miss" in this sense, so maybe try looking up "alone" or "longing for" or sth like that on Parf Edhellen. Hope it helps!