it starts from "Max throttle" and subtracts power regarding actual speed

timer programming

1) How do you mount it on your plane?

it is simply sticked on fuselage wall ... or you can see it on my indoor model ... the orientation must be that it makes impulses shorter if your model turns left - if not, just use the "reverse" switch and that is ... everything else is question of proper sensitivity setting (in gyro, in timer and afte all also in ESC if possible)

2) I know your timer is self-designed but would a Z-tron, JMP or Will Hubin timer work here??

no, everthing is in that one device, you not need any extra timer

3) How about a wiring diagram or schematic??

there is not schematics :-) ... everything is program in the device (as well as timer only and timer with 4-2-4 simulation) ... it has only connectors ... and to be sure one blocking capacitor, but I tested it all also without and never failed with switching BEC in Jeti spin ESC