If you aren't checking in bags, you should be getting there at 3:30/4 am. I've had early morning flights at Terminal 5 and it's surprisingly a zoo. Even worse in this past year due to staffing shortages. The lines are really bad at times. I'm grateful for my TSA Precheck.

Your flight leaves at 6 am, but you should be going by boarding time, not the flight departure time. There is no CLEAR at all in Terminal 5. The CLEAR website informs you of this. It's not even a guarantee that TSA Precheck lanes will be open by then