The Uzi is ok (although it maybe ought to cost more, since it is absolutely superb) but the Enchanted Sword is a bit too good, especially if more than one copy was available in the same game.
Someone dual-wielding Enchanted Swords would automatically defeat any monster apart from the Dunwich Horror. Adding 1 automatic success is considerably better than adding three additional dice (which is about how many you need to give a good expectation of adding an additional success ), so on terms of the expected outcome, the Enchanted Sword is the equivalent of at least a +6 (or better) one-handed weapon. AND, these weapons wouldn't be affected by Physical/Magical resistance, as they're not providing a bonus in the normal sense.
What you could do is have the items exhaust to add the successes (therefore only being useful against one monster per turn anyway) and require all the user's focus to refresh.
(Edited to add: sorry, you addressed some of these points while I was typing)