I have a suggestion: Don't email him again for at least a week or two. You don't want to put off a bad vibe right now. Stay calm and wait for them to contact you like they said they would.

Don't let yourself start to panic until it's been over a week. At that point it makes sense to send a short and courteous email letting them know that you're unaware of their plans and need to be filled in in order to make your own plans.

Give it a little time. You did well in the interview. They told you they're interested in hiring you. They may still be deciding between a couple people. Stay in contact with them, but don't hit them with emails every day. They should communicate with you their decision soon. If they don't (after giving it a couple weeks at LEAST), then you'll want to start taking different steps. But cross that bridge only when you get there, don't force it to come early by emailing them too much.

Hope this helps!