While I understand the 'meat' of what the BB says, I do not agree that a SO should be "included" to any great extent in the sponsor-sponsee relationship. In my case, and my husband's respectively, each of us have sponsors in our home group so we each know the others'. However, he is new to his sponsor relationship so I let him tell me about their talks, etc, as much as he wants to; I have been with my sponsor since I was about 5 mo sober (now 21) so the three of us have a close relationship. This is probably an unusual scenario.
I think trust and a lot of things sound like they are really the issue- AlAnon is a great suggestion. To me, your question about confirming the sponsor exists, etc, are like when my parents tried breathalyzing me regularly (I was living with them at the time)- it became a game of sorts with me always trying to beat it, or avoid it or proclaim its unfairness....
He's got to "do" all this himself.
Only you can decide if you want to proceed in what sounds like a hurtful relationship.
Take care.