How did the CoE and cannon law go from being created in order to let Henry VIII marry and divorce at-will, to (essentially) forcing Edward VII to abdicate in order to marry a divorcee?
The laws on divorce never changed. I have a number of past answers relating to this:
On royal marriages vs mistresses
On problems people had with Wallis Simpson
The tl;dr is that Henry had annulments rather than divorces, which is (generally speaking) the religious way of dissolving marriages - saying that they never really happened in the first place because of a mistake or later-discovered problem. But even if he had had divorces, there was a difference between the male sovereign changing from one wife to marry a noble/royal virgin and the male sovereign marrying a non-noble/royal woman who had been married twice before. The fact that Wallis was divorced was only half the problem.