Can all phosphites be converted into phosphorous acid by acidifying the phosphite solution? Swim also wonders what basifying the solution would form.

I would assume so. Acidifying most weak bases will get you a weak acid ;). I doubt basifying it would do anything.

Aren't phosphites salts of phosphorous acid though same way phosphates are the salts of phosphoric acid?

Aren't phosphites salts of phosphorous acid though same way phosphates are the salts of phosphoric acid?

Yezzir.