I think it generally hits a lot of good points, but a few things seem "missing".
Crafting magic items.
Getting a free magic item every few levels is nice, but it also feels kinda "off". It's hard to explain, I just feel like it misses out part of the idea of an artificer by regulating it the way it does. But until they create an optional rule for magic item creation / crafting that works out better and takes proficiency into account, it works fine, if not really giving the "batman making his gadgets" feel.
The major benefit I can see to this (if I'm remembering the rules correctly) would be being able to have two concentration spells running at once. The other benefit is allowing self-target spells to target other members of the party by giving them the enchanted object. Otherwise given the very limited spells available to the artificer, you're just pre-casting a spell, and hoping it's relevant during the day, when you could just cast it normally.
It would be interesting to see how it might work if the infused spells lasted for two days, to compensate for the fewer spells an artificer gets, essentially allowing them to double their spells per day, if they saved all their spells from the previous day. But that might get weird.
Attuned magical item bonuses
I like it, but it also seems to heavily rely on the game and DM, in a party of four, by default it's a total of 12 attunement slots, I'm not sure that bonus at level 5 is going to be relevant for a while in most games.
CR2 or lower companion that as a reaction to you getting attacked can attack your attacker. Seems pretty good, but I'm inclined to be wary when the beastmaster ranger's whole thing is supposed to be having a companion to fight with, but it doesn't get something as strong.
Some kind of delivery mechanism for the items, a sling/slingshot, crossbow, bow, nosgoth-esque grenade launcher. Being able to make something to extend the range.