Both your cbd and thc would be deprotonted under those basic conditions. This deprotonation is what aids in increased water solubility. Can you explain why you think thc will remain in the water layer and your cbd will not.
Cbd would have two free alkoxides and thc would only have one which would mean if both alcohols are deprotonated on cbd it would be more readily dissolved in water over thc.
For all, yes the pka of the phenolic proton is around 10 (the same as other phenol protons).