Listen, I think that this essentially boils down to if you trust your partner or not.

He is 28 - nobody gets led into bad behaviour that they morally wouldn’t engage in by a friend a 28.
At twelve? Yes. As an adult though? no.

From what you described, to me his behaviour checks out.

If I were you the one thing I would ask him to do would be not to lie, conceal or modify his behaviour to placate you.

If what he does is likely to worry you, then he can explain himself and reassure you.

You can build trust - what he did is the one thing that is sure to destroy it.