There may be a way to skip the cutscene that happens twice during each Anubis fight after removing 1/3 of his health, which would likely save about half a minute or more if coupled with better Anubis platform manipulation.

The second glider level has significant lag that could be reduced by minimizing projectiles on screen for about 5s of save, and given that there may be significant time save against Ra with more gun and bomb upgrade and baiting extra hits in the first phase of the fight, my estimate is that the TAS could go about a minute faster, possibly more.