...backwards engineering is maybe the hard way trying to decode the Dynapath logic would be a waste of time. The only thing that may help to convert to LInuxcnc is the "Installation Manual" for 40/50/60M units. They did cost 200usd from DP few years ago. just email them or call.
https://www.dynapath.com/services-faq6.php
This would show Pinouts on the Dynapath Cables for Servo's/Amps and spindle drive....but, DC I/O and AC I/O for relays etc the manual would not help. Only the original machine builder would know. Or have the schematics of wiring.
Note:
... about that ASSEMB30 program....its runs in DOS you need a Floppy Drive to run it or and x86 PC, FDD, and a LPT Printer Port..some functions dont seem to work right on a USB FDD on a Win7 32bit pc using Command Prompt window.
DJ