You are flying with a T.16000 flight stick.
This stick with buttons mapped for trim along with the keyboard buttons mapped for trim will not give you the fine control you need to adjust the trim properly.
If you try, you will be up & down.
To get the proper control, you need an encoder wheel (knob)
or an axis that will let you set the trim to exact level flight.
Don’t expect to be able to trim to level flight.