First of all, shout out to you for being supportive! We need more people like you in the world. I’m definitely one of those people where I don’t MIND if people finish my sentence for me, but I would prefer if they didn’t. What you’re doing now by just keeping eye contact though is perfect. The worst is when people look down when I stutter, it feels like they’re looking down on me. Now for bringing up him going to speech therapy is a tricky one. From what you said, it seems like me and your boyfriend are similar in how bad we feel from stuttering so it’s a sensitive topic. Before you bring it up you HAVE to make it clear that you don’t care that he stutters and you accept all him, especially his imperfections. If he isn’t comfortable with the conversation, then bringing up speech therapy may go south. Then gently bring it up if you feel the conversation flows that way. Now I don’t know either of you. But from my personal experience, I get super uncomfortable talking about my stutter even with people I’ve known my whole life so just prepare for that. Hope this helps.