First thing I would recognize is that it's unlikely you'll both find partners at exactly the same time. Each of you will have your own pace, and you can't try to keep up with the other, nor can one expect the other to hold back and wait for both to find someone.
The jealousy hurdle you mention sounds like insecurity. One way to help that is to reassure one another that you're still committed to the relationship, and to do special things together to maintain intimacy. But ultimately, dealing with insecurity comes from within. Many have been in those shoes, check out some Golden Nuggets
How do you know if a poly relationship is right for you? Same way you know if any relationship is right for you: it feels right. Cliche I suppose, but it's true. Oh, there are plenty of signs when something is wrong, I could write a novel on that... but if you've got experience dating, you know what many of those are for you.