Sounds like you won't know your work load with this until you've been in it 3-6 months. And if you are the "US Rep" they are going to forward every US call/email/situation to you. Whatever compensation contract you come to I'd request a re-evaluation every 3 months for the first year. You don't want to hire on thinking it'll be 10-15 hours a week and then find out you are really putting in 60.

Sounds exciting though! What a neat opportunity.