I too have a boyfriend who has a difficult time when I'm manic. He was with me when I was first diagnosed last February and it was very draining on it. Your boyfriend sounds a lot like mine with the, "just chill," they don't understand that we just can't "chill out" no matter how much we may want to.
I bought my boyfriend a book, "Loving Someone with Bipolar Disorder" and he's starting to read it, but it's hard for him to really get engrossed. Guys just like to "fix" things, they don't really want to know "why" we feel the way we feel, they just want us "fixed." Unfortunately it's just not that easy and it is very easy to get frustrated.
A lot of times my boyfriend will try to get me to focus and ask me questions like, "What caused you to start going manic? How long have you been feeling like this? What do you want me to do for you?" I have Bipolar II so I'm more hypomanic where I feel a compulsion to clean or reorganize things. Sometimes the paranoia gets the best of me and all he can do is let me rant and rave until it's over, but it's hard.
I don't know how much I've helped you, but try to get your guy some info on your condition, that might be the best place to start. Tell him what you need and don't need from him when a manic phase hits and just remember that it can be just as scary for the guy as it is for us, at least we know what to expect, our boyfriends don't.