Sounds like you're doing good and have a direction.
About Be... and please take this with a healthy bucket of salt - I don't think monogamously very well at all, and I don't tend to separate sex/relationships from life at large.
That previous line said...
For me, a partner I can depend on is one who will accept me as I am. Whether it is me leaving the laundry for the maid (or whoever wishes to do it) or me enjoying interacting with people I am attracted to. Definitely his comfort and acceptance is important to me, but I don't really place specially different points on whether I can't tell a partner that I blew my budget buying something I really wanted or that I am attracted to another man. If there is something I do or am that I have to hide from a partner for fear of the reaction (disagreement is fine, control or anger is not), I take it as a sign that this person does not have the capacity to survive a relationship with me with his sanity in place. Because I know I am independent minded and I don't take well to tiptoeing around people.
Having some areas to be careful of is understandable. When you bring two people together, there will be some give and take, some issues that impact each other and so on. It is your call to decide what is important to be accepted and how much. But if you're rescuing someone all the time and you can't count on them if you need a shoulder to rest your head on, you need to ask yourself whether you are looking to adopt someone or share your life with them.
In your place, I wouldn't assume what Be's response would be, but initiate a simple conversation about how you feel sometimes. See how he responds. If it doesn't go well, it was just a thought you shared, it isn't like you did anything. But you now have the information to see whether his reaction/response is something you can live with - or, decide how you will proceed with disengaging and finding relationships where you feel accepted better. You don't even have to conclude you are poly (though you sound like it) - simply describing what actually happened is definitely you. Can he accept you as you are?
I agree with you in a way, and I have to say the only reason I've been depressed and anxious recently is that I can't talk for now, I can't be myself, because I fear I could potentially destroy my relationship (and all that revolve around it, our families going well together, my young siblings who just adore Be as well as my mom, our lifestyle...) just by being myself.
On the other hand, with someone as damaged as Be I don't think it would be wise to say upfront that I may want to share my heart(s?) with several partners in the future. I always thought of our relationship as a slow work in progress and I was okay with it being a lifelong project. The idea was that, since we want to spend our lives together, we have all our time to help each other heal and grow, take baby-steps by baby-steps.
I'm curious though : what makes you think I'm poly ?