The Promo 150 uses simple up- down signals to make MACH move Z (works pretty good on a parallel port system). With the ESS there is too much delay between MACH and the actual position of the table to make real time feedback impossible. So WARP9 made two of the ESS inputs listen to the THC UP and DOWN signals and then do a Z move outside MACH then tell MACH about it after the fact. You have to have the USE THC checked and things set right in ESS Config to make it work. As far as the I/O on the 5 axis breakout you may not have enough to do homes and also the THC signals. Normal BoB only has 5 inputs and E-stop has to use one, THC needs three. Then you have one. The good news is that the ESS than handle up to three BoB's so you can add lots more I/O
The ability to restart a cut is more of a procedure (Skill) than . Its a series of steps you have to follow. It is somewhat dependent on the controls and the THC. Maybe when you write to Promo about how to use their THC with the ESS they can tell you how to restart a cut in MACH with their THC.
One of the real challenges of building a CNC Plasma table using an assortment of parts is they will not always work together and the vendors tend to avoid trying to support something they do not sell. As you have found you can spend countless hours trying stuff and with a lack of support never find the combination that makes it work.