Well, if I've built my fixture model correctly:
Assuming LUFC and SFC win all their games, leaving aside the 3 head-to-heads between them and us, their maximum points are:
SFC: 106
LUFC: 102
Assuming Leeds win the Leeds/S'ton game at the end of the season, then they're on 105, S'ton on 106.
So it comes down to the matches we have against them; if they both win these, then it's 108/109.
So, 109 points makes us mathematically promoted. 34 points from 15 games, or 2.27 ppg.
Going the other way, the lowest I can get us finishing is 10th, though I suspect I can get it lower with some fine tuning.