Obviously there are other issues here - I am thinking about his attitude to the unborn child etc - but really your DS has a massive problem with boundaries - my jaw dropped when I read many of your posts:
Have password changed multiple times, bought him and his sister (8) their own kindles and phone to keep them off mine etc.
They shouldn't EVER be on your devices - how dare they!
He had taken it without asking to play a game
He is the one at fault here then
went into my whatsapp and read my messages.
Has he any idea what a shitty thing that is to do to anyone, never mind one's parent?
I have talked to him about privacy
I think he needs a bollocking about privacy
but more worried about the effect on him of reading those messages.
Which wouldn't be a problem if he knew to keep his nose out of other people's private matters.
I did give him a mild telling off.
I would have wiped the floor with him
the kids always manage to get my passwords.
You make it sound like some kind of game - they should NOT be doing this AT ALL.
He has also repeatedly eavesdropped on mine and DH's private conversations about sensitive matters.
Obviously you need to be more careful where and when you have these sorts of conversations - but again, how dare he?
I would be getting a lot madder with him than you seem to have done so far and I don't blame your DP for being annoyed - you really don't have any privacy from this child. This is not your fault and I think a bit of righteous indignation on your part wouldn't come amiss.
That is not to say that you shouldn't get support for him for other issues - but I would try and get one of those fingerprint protected phones and come down very hard on any further breaches of your privacy.