I agree, it's going to be tight. I can be in the United Club by C terminal security in about 10 to 15 minutes after landing in BC using GE and carry-on. But if you have to wait for a bag, very risky for 45 minutes, a possibility for 1 hour 15 minutes. Make sure you get Priority tags on your bags, but they don't do much good at EWR sadly.
I agree with others, stay booked on the AM flight and take your chances of getting on the evening flight, although now you need to get your bag tag changed which will take a lot of time.
What I often do on a long Int. flight is check my flight status on UA.com on my phone close to departure time. Normally the pilot has figured up ATC holds, tail or head wind etc. at that point and updated the arrival time. Many times the long hauls are early which in your case is a plus. If it looks like you're going to be getting in 20 or so minutes early, I would roll the dice and switch to the earlier flight before departure.
Bottom line, this is EXACTLY why I never check baggage, even on a two week Asia trip, that's what hotel laundry is for...lol.