Future swinger couple needs some advice?

I am 18 and have a girlfriend who is 16. We are both relatively open-minded individuals. Because we are so young we have both agreed to give each other more time to grow up. In the meantime she has acquired another boyfriend who she enjoys to give foot jobs to. I enjoy flirting around to and some times can pick up as many as 10 girls a day. We have just spent some time away from each other, and are in a situation where we cannot really manage any time to spend together and just enjoy each other as a couple. This means we have not spoken to each other about what is appropriate and not appropriate to do with other people. How can I make moral-based decisions about what to do and what not to do with other people. btw, neither one of us REALLY know for sure what the other person is doing, its more of just feeling. I also think that it is important to have SOME level of intimacy with the person that you want to spend the rest of your life with. What do you think is a good level to maintain for intimacy and what is a good level just for sexual exploration.