I can play by ear, but I can't read notation/don't understand theory
Reading notation can open up a whole new world of gigs, and understanding theory makes reading easier, as well as being an aid to the composition process. Scales, intervals, and chords are most easily visualised with a keyboard instrument due to its straightforward layout of all the available pitches.
I have a BA in music from NYU, which was a great and necessary primer for my real theoretical education, transcribing music from recordings to the page. I can help you learn to sight read, as well as understand music through harmonic analysis.