I am not sure how to answer your question about how many contacts the average person makes in
the ARRL 160 contest. I would say that 100 to 300 contacts is pretty easy to do in this contest.
High scoring stations will make over 1000 contacts.
I would say that as midnight passes on the west coast of the USA things will start slowing down
but then they tend to pick up a hour or so before sunrise on the east coast. So I would think the deadest hours would be between those times.
You might try looking on the 3830 score rumors pages and see if people posted rate sheets.
I do not do this contest very often but here is one such rate sheet.http://lists.contesting.com/archives//html/3830/1997-12/msg00300.html
You can do some searches from here:http://lists.contesting.com/archives//html/3830/
In addition you might consider asking this question on cq-contest.http://lists.contesting.com/mailman/listinfo/cq-contest
I hope that some of this is helpful and that you have fun in the contest.