I m newbie to this..any help is appreciated.

I have an upcoming flight ZFV > EWR > SFO and return.
I stay around Trenton,NJ equal commute to amtrak station philly and to Newark international airport. The problem is the train to newark is night before to the flight at 8 am next day. If I were to take the train I will have to stay at the airport overnight and same while coming back.
If I don't take the train then I am breaking the trip and the tickets will be cancelled.

I am trying to figure out my best possible options without to stay 12 hours at the airport. Can you please advise on what if

1) I go to philly, park my car, get on amtrak and have it scanned by conductor and get off in trenton. Does this count as train trip? Then go home and in the morn take the car. For return exclude the train leg and just drive back in the car.
2) go to philly and take train all the way to Newark international stato on but not take monorail and stay in the hotel overnight.
3) skip the train leg and go to the airport directly.
4) just get the tickets from kiosk and not have conductor scan it.
5) Any possibility to call united to remove train segment from the trip.
6) if I were to do first leg as required and don't finish the second leg train journey, any issues with united?

Thank you much in advance.