In that case, I’m fairly certain you don’t need the outgoing transformation, nor the outgoing value format.
For my Tasmota dimmers, I use the same incoming transform as you. I do not define the minimum and maximum though.
You may have noticed already that Tasmota sends out the RESULT topic for many different actions, and sometimes they will not include dimmer information. openHAB will then complain in the logs that it can’t find the dimmer values. To get around this you can use a REGEX first which will only pass data on to the JSONPATH transform if the word Dimmer is present:
REGEX:(.*Dimmer.*)∩JSONPATH:$.Dimmer