"could" possibility for present

Are the following sentences correct with the word "could" to mean possibility?

Peter could be in the garden now.

Peter could be working in the garden now.

Peter could go fishing every day. I have met him at the river many times.

I am not sure about the last sentence. The first and second appear correct to me.

Thank you very much.

The first two sentences are quite normal, and their usual reading would be with the epistemic reading of "could" rather than the deontic. In other words, they are about the speaker's knowledge, not about possibility in the real world. So

Peter could be in the garden now.

is probably not talking about Peter's ability to be in the garden if he wants to, but about my lack of knowledge whether he is or is not.

This meaning is possible for your third sentence, but feels less plausible to me. It does depend on the context though; it would work in some contexts, eg

Peter could go fishing every day, for all I know.

(where the idiom "for all I know" conveys some irritation at not being told what is happening)