I have also had thoughts about things that I suspect were going on during the latter parts of XAH's and my marriage. Like you, I have no proof. Like you, I'm fairly certain I'm right, nevertheless.
But as others here have said, it doesn't make a difference in anything any more. In your situation, yes, you should get tested to make sure there are no "mementos" that could endanger your health in the future. But in my situation, any damage that was being done ended when we divorced. These thoughts are not productive or helpful in any way, and it's best that I just change the channel when they come up.