Thi i problem I've been trying to find a solution to as well, but
unfortunately I can't help yiu much since I only enamel copper and
silver. BUT- as far as soldered pieces moving, just make sure
everything is anchored just like when you hyave to do multiple
soldering jobs on the same piece and clean up the excess solder when
youre done so the enamel will flow over it, but the solder has to be
pretty close to pure metal as possible (for silver it's eutectic
solder-mostly silver but with a little copper I think to make it
flow but I don't know the equivalent for anything else) I fire enamel
at about 1450 F.
There is an article on the forum about enameling stones onto
titanium without using a stone setting, but I think he was using
diamonds or CZ or something. It may be worth a read. If I can find
again, I'll post it to you.
Rio Grande used to sell a gel to put on stones to keep them cool
while doing repairs and stuff, so you wouldn't have to remove them. I
don't know how effective it is at high temperatures, but that also
may be worth a look.
Be careful with torch firing though. Studio buddies of mine have had
problems with the enamel popping of after a few weeks. Something
about the metal not heating evenly or something. I haven't tried it.
I'm a kiln type of girl. Hopefully this at least made sense. It would
be even better if it helped.