If you want to go in F, then go via LAX.
If you want to go in J, then go via SFO.
Just book a 'normal' connection, 2-3 hrs, enough time to chill with a few drinks and snacks in the lounge, wash hands frequently, and you'll be fine.
Any precautions you take by avoiding lounges or arriving the day early will be completely offset by spending the next 15 hours in a metal tube with hundreds of strangers, so that is a waste of time, IMO.