The closer the better. You may set faults from the TR6 if you’re too far out.
Slightly advanced would be preferable to slightly retarded. I don’t recall which way was advanced, over or under.
It’s easy to adjust using a 14mm socket and a longer 1/4” extension.
Be sure your tach signal is trust worthy.
No, definitely must be off to adjust cam sensor. And be sure to snug up the bolt each time you adjust.
Clockwise to retard counterclockwise to advance. 1/16” is a good amount to move.
I've not seen that sort of thing, but how old is your TR6? About 2 years ago we changed the sync logic to be less sensitive, so you are probably fine where you had it.
I will try to duplicate that issue on my car and see what I get