OK then, half-conscious and semi-formed, an idea is trying to come to me...
By sacrificing a spell slot whilst infusing an item, you may instead apply the infusion to multiple applicable items within reach, up to the level of the spell slot sacrificed. This ability takes a full round action and is usable 1/encounter...?
Also...you may want to address the retain essence/'the only thing you've managed to break so far' issues. I still think retain essence is a far better ability, and if they already have retain essence then what happens to them at level 5 in this?
You really need to completely reword and revamp 'Artificer Abilities' too, you've added the bonus feats into the table already and it doesn't actually make much sense, although I think I get what you mean.
There's more...stuff, in the back of my head. But I've been working for 16 hours so I'm gonna go to bed and try to make my brain work tomorrow instead.
I may succeed.
Stranger things have happened...