No, this is pedantic::

De facto means in fact. Given that the king does no governing no, he is not, in fact, the ruler. You may be looking for de jure, though I question even that.

No, he's the ceremonial head of state. There's a polite fiction that all power comes from him, but he can't actually make anyone do anything.

If he tried, people would say no. If he insisted, he'd get tossed out on his ear.

The king of the UK still has to respect the Law. Being king does not mean that one can do as one pleased, or that there are no checks and balances. The last English king who tried to become an absolute ruler caused the English Civil War and was put on the chopping block by Parliament, as a matter of fact.