the idea of just munching on some cold butter in my mouth makes me recoil a little

This could apply to a lot of foods which you add little bits to enhance stuff. Chopped onion on a sarnie is amazing yet I'd be recoiling thinkinig of chomping some cold raw onion.

Not having salted butter may be why it makes you recoil too, unsalted butter is just tasteless goo..

As for the bread, Just the standard white bread.

As for the fillings, I wouldn't class mustard as wet, that would still fall under a spread category. Wet stuff would be things like Ragu or chilli, Ramen or any sort of pasta with a runny sauce. And you dont just chuck all the liquid on there, you'd use a straining spoon but the noodles and what not are still gona retain a lot of water.

If these sound like mental ideas, then it backs up my point you're doing yourself a disservice by not letting yourself explore a world of sanddwich just because you refuse to put a little bit of butter on your bread.

It could also be because I'm fairly baked and can't stop thinking about what sandwich to have.

I'm not sure what you're italian dressing is exactly but I'm guessing it's mostly olive oil, thats the perfect wet topping and your cream cheese is probably doing the work of the wet barrier.