So I am flying FRA-EWR-HOU-LAX on Saturday getting to LAX at 10:26 pm.

My FRA-EWR flight gets into EWR at 2:15 pm and EWR-HOU departs at 4:25. Since I'd prefer two flights rather than 3 and I don't need the extra flights for EQM, I am thinking I may do the following:

There are flights EWR-LAX at 3:25 pm and at 7:15 pm. Both have a lot of available seats and changing flights only costs $25 for Gold elite. I want to change to the 3:25 flight, but then I will only have 1:10 to go through customs. I am assuming that in case I don't make it, they will just put me on the 7:15 flight since that has plenty of seats. Or is that really too risky and I should just change to the 7:15 flight right away to guarantee a seat to avoid getting stuck in EWR? I guess worst case scenario, I'll end up on my EWR-HOU-LAX flight and just end up losing $25. What would others do in my situation? I would rather sit in EWR for 5 hours and get a massage/nails done at the spa than be on a plane those extra 5 hours.