If they are addressed to you both, then open them. If they are addressed to him, but pertain to joint accounts/mortgage/bills then ask him about them. I don't think watching out for YOUR credit/financial future is controlling. That is YOUR life too. Also, as far as the attorney goes, if you don't know what it is about then ask if you want to know.
I am NOT married, so maybe my ideas are off, but wanting to know about anything that relates to your well being is not being controlling.
Miss