I have this issue come up a lot when building boats, if you bring your wood/bartop in from outside, let it come to room temp for a few days before you epoxy. Also when you epoxy, due it at a point when the temp will drop only slightly right after you put it on. We usually do our epoxy coats on our boats in the evening to ensure the temperature will not rise, which leads to a lot more bubbles coming up out of the wood. I have not yet decided on a material for my bar top but I hope to avoid this situation as I do in my boats when it does come to that part of the process.
By the way, that is an exceptional look bar… nice job
-Zach