If he decides that friendship is not enough and quits contact, that will be a good indicator to me of what his true intentions are.
I feel like friendship is in fact what is best in order to have him in my life and not be hurt. But of course, I don't know if it's possible for us to take it over to that alternate level. Time will tell. I usually don't call him, so if he keeps calling me despite me closing the door on a physical relationship, I will take it as a cue to build our friendship back up. If he stops calling that will be an answer too.
Thanks. It's easier to find the right way when talking it out with someone else.