Hi,
That is correct on 1) in terms of customs. The luggage drop is after customs so they don't check the time there ... you just have to check-in at the counter before the cutoff (and then lug your luggage thru customs first). 630 is fine for that...I think the cutoff for check-in is 60 minutes.
I can't comment specifically on the processing time for security as I have Nexus/GE. However I don't recall Tuesday morning being particularly busy at that time unless it is close to some vacation/holiday. If customs is busy they do flow control and they restrict entry into the customs hall depending on when your flight is departing.
Please pardon the vagueness of the details but my direct experience isn't with your circumstances. My guess is that you should be fine getting there at 630.