Front hubs can be a problem for different reasons but at your power level it’s a safety issue; make sure you have good torque arms so that hub motor axle doesn’t break the fork dropouts. At the very high power levels (and weight) it introduces traction problems and worse handling. The way you got it is just fine and should be great to avoid pedaling to start the engine, and won’t affect handling or reduce traction noticeably.
I see you wanna just use the motor to start then switch to dynamo. That’s cool; oh I think you could setup the switch easily by simply having a switch for your regen brake. Usually a switch is put in a lever or off the caliper. In my tube frame ebike build I’ve got two mech brake switches one on the lever and one off the rear brake foot pedal. But mine wasn’t for braking it was for brake light. You could setup your controller for very low regen as needed.
Ive used a throttle for variable regen brake for 5 years, and it’s always been, I get 5% back of what I put in to get the bike moving, to stop it. Was a couple miles on the last one (40 mile range).
