Nice threads, and you're not the first to go down this path. FYI, your lathe locks out the half-nuts if the cross/longitudinal feed level is engaged (and vice versa). That's a common problem also, "I can't get my lathe to engage the power feed". Turns out the half nut lever is very slightly engaged (not enough to engage the half nuts on the lead screw) and locks out the power feed.
Bruce