The worst nonsense of the story, "(a trick we may need in a few billion years)".
To require that, we'd need to add around four times the sun's current mass (off the cuff estimate), to account for losses during the red giant phase and still retain 2.5 solar masses.
Then, a bit of magic to make the numbers still work...
Sol can *never* go supernova, save if another star rams into it and that star has enough mass. And well, we'd have worse problems than trying to outrun a supernova. You know, like ejection from the star system. Or ramming into either star as our orbit is turned into rubbish.