The easiest workaround is to adjust the yawsensitivity until the multiplier is close to what you want:
https://www.mouse-sensitivity.com/?share=d76e950113b97a0a2545cc2c1dd41d97
In-game sensitivity is meant for those who do not want to mess around in config files.
If you provide a MouseSensitivityMultiplierUnit and instead calculate the MouseYawSensitivity it will be very inaccurate since there's no decimal support for it.
The calculator will give you the most accurate and precise sensitivity for your conversion when using the config file, there's really no reason to change the hipfire sensitivity in-game afterwards? If you want to change it, do a new calculation with your new preference.
Note that you can manually adjust the Sensitivity 1 (MouseYawSensitivity) in the config file calculation until the MouseSensitivityMultiplierUnit is calculated to be close to what you want.
Sorry, thought you meant ADSMouseMultiplierUnit. MouseSensitivityMultiplierUnit is being calculated to give you the most precise sensitivity for hipfire, so it wouldn't make any sense the use an existing value. I could make an opposite entry where you enter your MouseSensitivityMultiplierUnit and MouseYawSensitivity is calculated instead, but it would be really inaccurate in comparison.
They are interchangable, but the values depends on the aspect ratio. For 16:9, MDH 100% = MDV 177.7778%, while MDV 100% = MDH 56.25% etc.
For 4:3 it would be MDH 100% = MDV 133.3333%, and MDV 100% = MDH 75%.
You have done it correctly, although you should technically use MDV 178% and not 177.7778% to match Relative Coefficient 1.78, but this will not make a discernible difference.
That is what you should put in the config file yes, and for scalar 0 you have to choose between the two options depending on what you prefer.