You hit the nail on the head. This happens to consultants all the time. All you can do is advice (I know you're part-time but it seems you sort of function more like a consultant than staff) and let them make their final decision. He has an idea, and wants someone to confirm his idea, rather than understand the real implications of it. It's his prerogative to employ the idea, but at least you have on the record that you advised differently.

You said this guy was new, it sounds like he doesn't value your opinion. I wonder, if he ignores your advice because you're a woman? I don't know enough about the situation to say if it's the case or not, but for some reason I get that feeling. I have worked with far too many men who, without even realizing it, disregard advice because it comes from a woman, and, when hearing the same exact advice from a man, all of a sudden see the logic in that advice. Just saying. Gender bias is real. But I digress.

Keep doing a great job at the new gig, and keep looking for full-time or another job to replace this one. Sounds like you need to call it quits with them anyhow. They aren't listening to you or using you to the fullest extent of your abilities. Why would you want to stick around for that?

Seesaw