Mike,
Of course I would never rise to the bait and say "told you so."
Sorry about that. I think your oven will make great pizza for years to come, and I am looking forward to hearing about it, and seeing your pizza photos.
Have you send a final photo of your oven? Also, how is the hearth temperature holding up? Is that working well?
My experience is that brick ovens just crack. My first Scott oven cracked in the vent, and after a few years, I lost half a brick in the dome. There doesn't seem to be anything you can do about it, and I have heard the "normal result of thermal expansion and contraction" speech quite a few times from professional Italian builders. That said, the precast ovens should not crack, but my guess is that you have little hairline surface cracks. It really isn't a problem. As others have noted, if you are not losing smoke and hot air out the top, your will be fine for years to come.
Cook, eat, enjoy and send photos.
James