Determine if phototransistor is in cutoff
That all looks fine.

You have current limiting on your LED. If it's an infrared LED it will have a forward voltage drop of about 1.4 V which leaves 1.6 V across its resistor. The current will be V/R = 1.6/100 = 16 mA which should be fine.
Your 10k resistor on the transistor will limit the maximum on current to 3/10k = 0.3 mA which is also fine.

I would have suggested using hysteresis but you've addressed that already.