Itchy, you're not giving a whole lot of detail - which is your prerogative, but it's unclear to me if your husband IS actually a bit of a controlling bastard, or if it's just that somewhere along the line the financial aspects of how things have been set up have just been mismanaged and misunderstood through ignorance rather than malice.
You say you're generally happy. You say in your opening post that your DH has "lots of" the finance accounts in his name (not all?) and that he's happy for you to check them.
There's all sorts of reasons why the passwords might keep changing - I reset things if I've forgotten frequently, and it happens more if it's a log-in I share with DH like the bloody broadband account, because either of us might forget to update the other that we've clicked the "forgotten password" link. The 2-step verification codes are annoying but that's not your DH's fault.
You must have bought groceries and what-not without a joint account card so you clearly have had some sort of system going about the money. He's not stopping you knowing what money there is in the marriage.
The deeds thing is concerning but again this could be a well-thought out financial protection for him leaving you vulnerable or it could be that he just took someone's word for it that this document needed signing and thought not much about it.
You haven't said he's controlling or you feel hard-done by, but a lot of posters have shouted loudly about abuse. Do you think you might be being financially controlled or abused, or do you think it is just historic reasons for why the accounts are mostly set up this way?
You need to educate yourself and protect yourself either way, but how you approach it is going to need to be different depending on what you feel about how your husband behaves to you.