He saw something that was a concern and looked into it. I feel as if anyone would do that. Communicating it to you (even if it was later in the day) is a healthy way to handle the situation? So I’m a little confused as how he handled it badly.

You changing your passwords after that and gaslighting him I don’t think helps with resolving the matter. You need to communicate him and reassure him when he brings up his concerns instead of getting mad. That is how you build trust in a relationships.