Knightsaber, perhaps it will help to remember that one person cannot always be "all" or meet all needs of another. I consider this the very essence of poly.
The topic which comes up from time to time when I discuss alternative relationships with "mono" friends is that I'm somehow cheating my wife by not asking for a divorce before persuing other relationships. Honestly, I think the opposite is truth. I believe the other relationships fufill needs not being met inside the marriage relationship both non sexual and sexual.
I'm new to trying to understand poly too. The one truth I have found is that complete honesty in communications both helps and hinders the journey, you have to accept that jealious is part of the emotional package. We all need to keep trying.
Intimacy without sex may be one option you could consider for starting new relationships. Everyone needs to be comfortable in their relationship status before the passions ensues. In my view, it gives you a safe corner, if challenges force changes in the relationship.