Sure, that’s fine. I don’t think it’s as elegant as making Infusions cost spell slots, but it works.
No, I’m sorry, it doesn’t. A spell is a spell, and a magic item is a magic item, and the class as it currently stands uses its spell slots to produce the former. You can pretend it’s the latter if you want, but that’s not consistent with the way the game mechanically expresses those things in any other instance, and it’s also not something you need an Artificer class to be able to do.
Mechanically more explicit? Yes. Clunky? I don’t believe it has to be.
There are plenty of counter-examples to this in published material. Ki abilities. Channel Divinity. Wild Shape. Racial features like the Eladrin teleport. Most relevant to this discussion, potions, scrolls, and wands.