What should non-stutterers know about people who have a stutter? What should S/Os know, and how are your partners?

What should non-stutterers know about people who have a stutter? What should S/Os know, and how are your partners? Hi everyone! Hope you are doing well. I just wanted to ask this question since I'm currently in a relationship with someone who stutters (and I really love him, so proud of him) but sometimes I feel like I offend him unintentionally...whether it's finishing his sentences without thinking (I actually do have ADHD and impulsive speech is a big problem, it's gotten me in trouble in many areas of life :/), or something else. I also one time told him how proud of him I was, bc he's accomplished a lot in life, and didn't let his stutter hinder him. I said, wish I could trade, I'd rather have that than ADHD (yeah I know stupid right? But honestly having ADHD had really messed up my life, and it just seems like ppl don't take it seriously. Just look at r/ADHD if you think that...ADHD affects everything in life I'm serious.) and he got really mad at me and said "it's nothing like that! You don't get it. I don't need someone to admire me." And I felt really hurt, but I do want to understand him better...so what are some things that we should understand? I already know finishing sentences is very bad (trying but hard for me to control I interrupt incessantly sometimes without even thinking :(...). Thanks!