I think it is perfectly normal for some of us to be anxious trying new things. I am kind of like that too.
If you are a fan of Doctor Who, remember that "fear is a superpower." If you don't know what I'm talking about, it's a silly science fiction show where they are facing some killer aliens or something and the advice refers to the fact that fear serves an important function for us: it keeps us safe, by, for example, preventing us from eating and drinking all kinds or random things.
But just rest assured that kava is perfectly safe, so long as you don't mix it with things like alcohol or Tylenol. A tablespoon is a fine dose to start with: just chug it down. It won't hurt you. The worst thing that is likely to happen is nothing at all. Maybe use less water to make it more concentrated. Then wait 45 minutes and see how you feel. Repeat if needed, but don't use more than a couple tablespoons to begin with to see how effects you.
It's true that Moi is not really the best strain for anxiety, in my opinion. I prefer KWK borongoru for that. But in small doses it can be helpful. On the other hand, I have heard of some people who really like Moi for anxiety. It is very potent, though, so moderation is key.