PX4, single motor (fixed-wing), power from 0 to 100 in 30% of the throttle range

Hello,

I’ve PX4 v.1.14.3 on a fixed-wing with a single motor (which I never had used before).
I calibrated the ESC, but the issue is that the power goes very quickly from 0 to a fixed speed (max motor speed I assume), and this happens both in QQroundControl and in the RC transmitter’s throttle stick, in a very short move…

It starts rotating at approximately 20% of the stick (pic 1 below, also, this is also weird, at 15% it does nothing), and it reaches the max speed at about 50% (pic 2 below), so, only 30% of the total move to control the motor, I think it cannot be right.

20%, it starts rotating, below here, no rotating:
image

50%, probably high speed, above here, no changes:
image

I tried to tune some parameters, as PWM_MAIN_MAX, PWM_MAIN_MIN and FW_THR_SLEW_MAX, but I couldn’t get better results…

image

Do you have some idea about what it could be happening, and which parameters I could adjust, or if there’s some tuning guide somewhere, please?

Thanks a lot