Wow. That's a lot of interaction. Her 'knowing' she's right and you defending your point of view.
You realize she's trying to be unreasonable, right? The living arrangement seems to be not working. You're not only trying to co-parent, but you're both occupying the same house. At different times, but still, the same house. If you both were truly living apart, this conversation wouldn't be necessary. You would have what you needed when the kids were with you and she would do whatever it is she does when they're with her.
Why didn't your son tell you he preferred the pills instead of the chewable ones? If he told her, he can tell you.
It is clear to me why you two are headed in the direction you are. She's done. She's not going to make things easy. She even said as much when you talked about all the court related issues - according to her, you know how to make it stop. Give her what she wants, until then she'll make you miserable and drain your finances. She's also got OM, so her energies are further spread out.
You're never going to be 'right' in her eyes. Nor should you try - that's circling the drain. But you are valid in your concerns. Do what is right by you and your kids. Maybe you 2 should switch from taking turns buying stuff to buying the stuff you and the kids need when you are together. That's probably unrealistic to be honest, I feel this sharing the house is making things more difficult. Is there another solution?
Her comments regarding the legal stuff bothers me, for some reason.
