I very much like what you wrote in your reasons for choosing poly. Really down-to-earth and honest. Thanks for sharing.
In my marriage, I'm the one who brought up being "poly" first, and my husband was somewhat forced to either accept it, or leave. I'm sure he feels much the same way you feel. And I do, too, about many of your points - especially about keeping the family together, maintaining your lifestyle, learning to be more independent and know that you'll be able to take care of yourself if you need to.
And just being able to say that you tried your best to make it all work and be successful... that counts for so much. So many people, mono or poly or whatever, simply don't do that. It's about putting yourself out there and willing to be vulnerable so that you can grow. That's great.
I hope you and your husband discover lots of wonderful things in poly together. Good luck on this journey!