Hi Butterfly Waterfall,
Welcome to our forum.
It sounds like you're moving in the right direction: first of all, toward more-emotionally-involved relationships which is what you wanted, but more importantly, toward relationships that are conducted with the knowledge and consent of all parties involved. Honesty is definitely the best policy!
It's understandable that W has those insecurities; help out as much as you can in the way of giving him reassurance (and keeping in touch with him regularly). But hopefully he'll come to understand that polyamory isn't about "replacing" people; it's not like monogamy where you have to leave one person in order to be with someone else.
Anyway, I'm glad to have you aboard, and wish you all the best.
Love means never having to say, "Put down that meat cleaver!"