[Can I build my own remote harness? Yes.] I have been unable to find the male end of the cable, so I tore up an PMD to make an extension, just to scope the PMD.
[What kills these PMD’s?] You forgot to mention the transistors are rated at -100v piv(peak inverse voltage) and there is a -80v spike generated when the FS opens after being driven by the PMD. I suspect this may have an effect on the life of the PMD.