What are the chances for Fast Track authorization passing at all?
The current House can barely manage to pass the measures necessary to authorize borrowing of money to fund the payments they have already authorized. Only Senate approval is required to ratify a treaty but it looks like the House has to get involved to pass fast track unless certain folk are grandstanding.
What are the ideological points that might block passage?
Gumming up the Senate is usually pretty easy. Particularly for a treaty where the Senate requires a 2/3rds vote. The Senate has rejected a whole slew of treaties that are much better for the US than any other power, including the UN law of the sea treaty update which the US has not ratified but still uses against other countries.
But even rolling rocks downhill requires that the people doing the pushing are going in the right direction.