Yes, on the ability to clear C security with an A departing boarding pass. Easy with two UA BP's, though I have done it with US.
Might I suggest, instead of going to the club, that you instead have a nice, peaceful, leisurely dinner at one of the nicer restaurants in Terminal C. By the time you get through customs and immigration (in Terminal B or C), it will be 2:30, maybe even 3:00.
Would be much better off spending $100 on dinner, versus only 90 minutes in the club.