Does the journal editor have authority not to publish my article after clear acceptance?
If they've accepted it, they will publish it (eventually). They have nothing to gain otherwise by holding your paper. That it's not been published in the latest issue isn't a sign that they're not going to publish your paper at all - they could for example have a lot of papers that are online ready waiting for an issue, and they've hit their page count limit for this issue.

Whether the journal has the authority to reject your paper after accepting it is a separate question. In principle, they can: nothing gets published without the editor-in-chief's approval after all, and he can change his mind. In practice, this happens extremely rarely. If they find out for example that the paper is plagiarized, then it can be rejected. But to reject it because they changed their mind about whether it's publishable - that's almost never going to happen.