[34C]

You are adding unnecessary complexity. Try using the LS150 output with the pair of diodes to rectify (to half wave DC) exactly as the Lenz diagram for the point motor. I would be surprised if that did not operate the uncoupler adequately.

 

[34C]

But you don't need a point motor to set addresses. Page 26 of the manual explains all. It's really neat, just set an address on the first output, and the other five are incremented +1 with unique addresses.

At this point I should add that unless you really really need remote uncoupling, I wouldn't bother using this or any other decoder. Typically uncoupling is performed in view of the operator, and a simply 'push to make' sprung button is all that is required to energise the uncoupler. My Kadee electromagnets are powered by depressing a piece of phosphor bronze strip onto a brass screw head to make the power circuit. This is cheap and simple.