Excellent and vulnerable piece, thanks so much for sharing. I've been some variation of swinging or poly for 20 years or so and knock on wood, have always remained STI free. I won't make ignorant comments like some about not using protection when necessary (because whatever you and your hubby choose to do is most assuredly up to you!), but I also won't say there has never been a time my partner and/or I didn't use protection. It sounds like you guys have the right ideas and for the most part are as safe as possible. I think you'll be just fine.
And I'm right there with you when it comes to being with a woman, there's just not much like it! <3