What you could do is get to Abu Simbel in the evening or afternoon and spend the night at the Seti (about 15 min walk from the temples). Get the ticket the night before so you can go straight to the security and entrance point. Or take the 1st flight that arrives. Leave at 9am back to ASW or LXR.

Book the Seti well in advance as it's often sold out (group bookings).

The train runs ontime, by airline standards. At least gets into Cairo within 15-30 minutes of. Is Ramses station on the east side of the Nile north of Cairo? I'd say it should be 30-45 minutes to CAI from there so it should be enough time. Take the early train if you are concerned. Most tourists appear to get off at the 1st Cairo station on the west bank.