The design seems to be extremely sensitive to any changes in the parameters.  Just for fun I swept the VCC from 11.25 to 12.75 volts in steps of 0.25.

The zoomed in step from a high logic level to the low logic level shows that the 12 volts (cyan)  have a much larger difference between logic high and low than the others.

Changing other values have basically the same drastic effect.

This dosen't fill me with any great hope to get this working with actual parts, but I'll for sure try it regardless.