And I thought my 2017's 6.95 60 was good for a catcher. Your son definitely has exceptional speed and arm strength. Sounds like he has a bright future.
In response to your questions.
#1 in general, the coaches want to see the swing so a walk, unless the pitches are woeful (which can happen), at best is a wasted opportunity. Try to square one up and if that is the first pitch, go for it. If a breaking pitch, probably lay off unless it is a cement mixer. If your son has legitimate power, I'd say swing for the fences (within normal swing). If he's more of a line drive hitter, try to hit a line drive.
#2 If they will "take" that time, than why try to improve? If it is a nice field and he's feeling frisky and confident, running it again, even if time goes up a TAD, would still be very impressive.