2) At the very least, the worldwalking power should probably require you to pay Fate to make up the difference between the item's strength and the local barrier rating. Ie, if the local barrier strength was 7, the power would fail unless you were willing to toss in a Fate point to make up the extra +2. It might even be necessary for you to have an aspect to invoke in order to spend each Fate. (Of course, as a Wizard you'd always have at least one, but unless you had one or more others that were appropriate, it would limit the maximum barrier strength you could get through by limiting the Fate you could spend.)
That seems like a pain in the butt having to figure out the local barrier strength every time. That's why I was going to propose to my GM we say it "just works". To be clear, I was going to propose ignoring the rules on this matter. Assuming that the rules are just a guideline. Making an item that's slightly outside the rules. That is to say, very deliberately not doing it like you just said even though that's RAW.
I was thinking it wouldn't be a big deal since as a Wizard he could open up passages to the Nevernever anyway. You do have a point that there's an actual "Worldwalker" power, though, and it's probably unfair to duplicate that with a mere enchanted item. Hmm. Need to think on it. Then again, Worldwalker says that if you're a wizard, you probably shouldn't be worrying about that power anyway.
3) Keep in mind that going blind into the Nevernever is entirely likely to put you into a worse place than you began: because now you have the local denizens of the Nevernever in front of you ... and possibly the same opposition you were escaping from following you into your own gate.
This point of view gets pushed so much that it actually had a bad effect on our last Dresden Files game where all the players were terrified of the Nevernever and were never interested in going there. I think it's because every time the topic comes up, everyone is all to eager to say how going to the Nevernever is no escape and can never lead anywhere good and won't help you in any way... yadda-yadda. It does get laid on a little thick!
I think going to the Nevernever needs to be made a little tempting too, so that it might sometimes seem like a good idea. Jumping in with such heavy negativity like, "Don't expect it to do you any good!" just seems to kill interest.