As you still said... For things that can be easy set to a axis in the Sim Controll settings itself ( Like Throttle, Flaps and so on) it is more intuitive to use a HID Joystick Controller ( Like a LeoBodnar , a Arduino with a Joystick Firmware or simply a existing real joystick).
Whatever.... For sure its possible also with Mobiflight !
The problem you got is the "transform" of the analog Poti Value ( 0-1023) into the needed Data Value for the FSUIPC Offsets where you make the input commands.
Those are mostly 0-16383 or in case of throttle and possible Reverser they start at -4096 (minus).
For FS2020 we use a different interface to the Sim (No longer FSUIPC Offsets .... Here we work with WASM and RPN Code .
The big benefit.... There we can do this transformatioin calculation logics within the Code we send.... All internal so the user not need to think about that.
For FSX this is not possible.... So YOU need to calculate this stuff by hand and write the needed Formula in the "Input Value" field of the Config Line.
The Poti gives 0-1023 ..... You need for the Sim Value 0-16383
In the Input line you can use the "@" symbol that represent the Poti Value..... and you multiply it with 16.
So Input: @*16
Result: MF send now the right Value.... e.g. Poti in Middle Position = Poti Value 512 .... 512*16= 8196 .
Target: You must make a math calculation that use the Input Value of Poti and result in a clean Output Value as expected by the Offset!
Give it a try.... If it not work contact us on DISCORD.... https://discord.gg/99vHbK7
There are lots of Users who work still with FSX and can help you !