I wouldn't keep one guinea. Separate them for a few minutes, and you'll see they both get VERY stressed.
I'm not a believer in keeping a bully around myself, so if I were in your shoes, I would do one of a few things. 1) Cull the male (or re-home him if you can) and get another female or two. 2) Re-home both 3) Separate them both from your chicken flock if that's feasible.
Guineas have a lot of common traits, but each one has its own personality. What do you mean by terrorizing? Is the male guinea drawing blood from your chickens, or just running them off without harm?
If the male is drawing blood, then you have to do something quick, but if he's just running the chickens around the yard - running them off 5 or 10 feet and then turning back to what he was doing before, then that's just dominance.
Is he doing it in a shared pen or while they're free-ranging? If they're sharing a pen or coop, then they may not have enough room to "go to their corners" so to speak.
But what I wouldn't do is keep just one guinea. Sometimes finding the right mix of personalities can be difficult, but try if you can to find your female another companion or two. She won't be happy by herself, even if she hangs with the chickens peacefully. There's always the option of all-in and building a flock of about 7 or 8 guineas. That's actually the best option if you can swing it.
Did any of that make sense? I'm only on my second cup of coffee - I'm not much good until my third

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