Making a triac phase control circuit - are my values correct?

[Zero999]

I thought MT1/MT2 can be flipped since the current runs both directions?

No, the gate drive always have to be relative to MT1. Most TRIACs will trigger on all four quadrants i.e. the gate current can be positive or negative, with respect to the voltage on M2, but not all quadrants have equal sensitivity. Some TRIACs will not trigger on all quadrants. Check the data sheet.