I am having a very similar issue to this (see: Help with Aeotec Nano dimmers and retractive switch).
I started off the same as the OP but have managed to get the lights to switch on/off and dim from the wall switches by setting the min/max brightness parameters to 5 and 89 respectively. However the dimming isn’t quite as smooth as I would like it. There is a noticeable series of very brief lags as the lights dim down when I press the button to switch them off or hold the button to dim. If I dim manually from the ST app I also find there’s no real noticeable dimming in the 100%-75% range. When I move the dimming slider below 75% the dimming becomes perceptible, but again there are short lags, as if the dimming is going 75,74,73,65,64,50% rather than smoothly transitioning from 75-50% in degrees of 1%. Has anyone else had this issue and managed to solve it?