Even if he concierge at the Hilton will do this for a nice fat tip, this is cutting things close. The check-in deadline is T-60, meaning that OP has 90 minutes to make it through CBP, to the Hilton, collect the box, drag it to UA, wait in line, and check it. He then has 30 minutes to make it to his gate.
All it takes is a wind shift, a bit of weather, ATC issues or whatever and he will lose his window.