Is there a way to stop keyboard.overruling my spelling and word choices?
Go to the Settings on the phone, then scroll down to Languages an input - Tap Virtual keyboard, the Google keyboard (if that's the one you are using).
Tap Text Correction, and turn off the options you don't want, like show suggestions, auto correction, etc - or adjust them so they work as you would like them to.
Go into the keyboard settings and adjust it.