WELCOME!! First let me commend you and your husband for being together for so long! It's always nice to see longevity like that.
As far as your questions go, you answered your first one! Well, at least as far as I go anyway. LOL Love, Trust, and Communication are the foundations to any healthy relationship and these are absolutely essential in a poly one. I'm a MASSIVE fan of communication even the uncomfortable type. They are all necessary to making this work.
I don't think trying to find a 3rd is futile at all. My wife and I have been living with our SO for the last 2 1/2 years and it's been amazing. It wasn't something that we sought, but rather had fall into our laps. This is a great place to meet like minded people and once that happens you never know!
I wish you luck and please keep us posted.