I'm like you and have asked myself the exact SAME questions over and over again for years
Two insights I had on the way:

- The people who seemed to get really uncomfortable with my being emotional had their own troubles they didn't or couldn't talk about at that time. Of course I only found that out later. It isn't always possible to listen and communicate when you have your head full

- It is really hard to read someones behaviour when there's lots of emotion involved. It IS stressful to deal with another person's emotions.

So I constantly find myself on both sides of the table. I try to understand the other person, but also I refuse to give up on expressing my feelings. On the other hand, I can't be a good supporter at all times myself. To a certain extent, to have authentic relationships it is necessary to talk about the real stuff I think. But it has to be a process in which both parties need to show respect for boundaries.
Just my 2 cents Thank you for starting this thread, I'll be following!