I think this is right. But also, I usually try to point out that multiple interpretations can be correct, and even a single event can be both historical and symbolic. I've never heard a Christian respond positively to that. If people want the mark to be a chip, or our phones, it can be, while also being our actions, while also being the debased coinage of the Romans. But none of the physical versions could happen without the internal mark, so your interpretation seems most correct to me.