I thought you'd stopped posting. I didn't realise you had a thread going here until you popped up on my thread (and thank you for that).
What odd behaviour from your husband. How very very strange.
I can't say my H has done anything like this before, but we're all different. I think what's more important than what your husband is doing or why he is doing it is what your boundaries are, whether they are working for you or not, and if not, do they need tweaking?
I know if my H was sneaking around looking at my journal or looking at my phone I would be furious. I'd let him know in no uncertain terms was he to do it again.
Do you want suggestions in how to respond to his intrusive questions? H HAS done that kind of thing with me before. If he's insinuating something, I pretend not to understand. It is probably not the most mature way of going about things, but it leaves his feelings with him and not with me.