desmobob

I've always figured that line diameter has way more influence on crankbait diving depth than the  mono vs. fluoro thing.    
 
If you want max depth from your crankbaits using monofilament, spool up with 8lb. or 10lb. rather than 12lb. and/or look for the brand or type of mono that has the smallest diameter for the pound test you want.
 
Bass don't seem to be line-shy.  Line visibility is probably the last thing on my list of concerns when choosing line.  (Except maybe when fishing for smallmouths in a crystal clear lake.)

Yes.  Choose the conventional sonar screen, then keep turning up the gain until the thermocline shows.  Same as with most any unit, as far as I know.

New tip-top.  Very easy to replace.  Contact your rod manufacturer to find the exact replacement type.  They will probably be able to send you one (and if you're lucky and they're good, a free one!).  Always keep a pack of assorted tip-tops around for emergencies!  They go on and off easily with hot-melt glue.
 
I just got a new one from Kistler after I "shortened" my new KLX UL spinning rod and somehow lost the little section that broke off.  In the mean time, I had an emergency back-up in place.  It didn't match at all and looked awful.  I'm glad the proper one came quickly
 
Tight lines,
Bob

I used to use snaps almost all the time, until I lost a monster bass when one opened.  Since then, I tried the Mustad "Fastach" device.  Not really a clip or snap; more like a fancy loop.  I've been using them for over a month now and have just ordered more.  I like them.
 
I don't notice any difference in fish catching.  Some lures benefit from having the nice, round loop to swing, shake, wiggle and swim from... it doesn't cramp their action at all, and offers more freedom of movement than even loop knots.
 
Tight lines,
Bob