I would say that your suppositions are, for the most part, wrong.
In most cases, cases are sold because the movement was parted out for use in a franken. In these cases, the condition tends to be good. But if the seller fails to post good, clear pics of the entire case, he/she is trying to hide something. As always, buy the seller before you buy the watch.
I was thinking the same thing, but I am more ambivalent about the dial & position of the date wheel in the date window? I have not seen enough (verified) 1665 service dials to make any final judgements, but my gut tells me something does not look right there.
I think I recall seeing it, but I cannot say for sure where? I also have not purchased any reps for quite awhile, but, when I did/do, I generally only deal with Andrew, Josh or Yuki, so you might want to start there.
As long as the watch is fitted with all the usual gen upgrades (crystal, crown/stem) & a good, reasonably accurate dial, most indy gen watchmakers (not a Rolex service center) will service it since few will be able to ID a gen-powered watch as anything other than a gen.
PMWF insert (1665 & 5513 inserts are interchangable)
Unless you are replacing the insert on an MBW, I would recommend that you measure you existing insert to be sure the PMWF insert will fit (there is little consistency between reps).
The quality of aftermarket hands is poor, so I do not know if another set from another seller will guarantee better results. As is the case with parts from DW, alot of this is luck-of-the-draw. You could order another set from another seller, but I would say there is a 50/50 chance that you will end up just repairing the hands.