Yes. You really have no reason to do so, unless one account is incentive-based, and the other is not.
Yes you can open another CJ account.... You can use seperate CJ accounts for each websites... its upto you... no probs... I have multiple CJ accounts....
Yes, I have contacted CJ support and they said it is completely ok to make 2nd incentive based acc, but I will need to use another email for the 2nd account.