Ortho-effect in substituted aromatic acids and bases
I'd like to throw a tentative explanation for the ortho effect into the ring:



In the molecules in question, an interaction between the protons of the methyl group and the lone pair of the amine nitrogen and the negative charge on the carboxylate, respectively,  can be assumed.

In the first case, the electron density on the N atom is (slightly) reduced and thus the basicity of o-toluidine.

In the latter case, a similar interaction provides additional stabilisation of the carboxylate. As a result, o-toluic acid is more acidic than the isomers.