Coolant temp sensor seems like a strong possibility - maybe the computer thinks the car is cold and keeps the starting mixture too rich. Make sure you are testing the CTS under the #3 intake manifold runner. You can also have a bad wire or connector back to the computer.

If the cam is out of time vs. the crankshaft that would explain why you need so much advance. Setting the cam with the lobes "up" and centered on the cam axis only works if the intake and exhaust timing are concentric around TDC. The cam timing would also have been affected by milling of the cylinder head.

Out of whack cam timing could affect the vacuum signal while cranking, maybe leading to too high fuel pressure from the FPR or other problem with the mixture.

Don't the crank and cam sprockets have marks on them that align with notches in the timing belt cover or the housing so they can be set independently of the printing on the timing belt? The manual should cover.