So, from what you said, FI is upset because of how much responsibility you have. Is that because it takes up all your time and you have none for him? Do you have kids and he's upset you don't spend time with the kids? Is he upset that you do all the work and no one else does? What exactly is he upset about?
Why I ask is that I am similar to you. I have 4 boards of organizations that I serve on. I am very passionate about every single one of them. Yes, I do have to devote a certain amount of time to them, attend events and so forth. My FI knows very well that I love what I do and he fully supports me, by attending events with me and becoming involved in a few of those organizations. It's something I made clear when I accept these positions to him is that I want to do these things and they are very important to me. But I also emphasize that our relationship is important also. Maybe I am lucky in the sense that FI doesn't make me choose.
I typically stand my ground for things I am passionate about and serving for a fundraiser would count. FI should feel lucky enough he doesn't have cancer and you are out there trying to raise funds.