Here's how to figure out if a coach is interested... they tell you to call at a certain time and they answer your calls. Another way to figure out if a coach is interested is if they ask for grades and have you fill out a financial aid calculator. Until any of that happens it means they like him as a player, but not until their Plan A makes a decision on what he wants to do.
Another thing that gets spread on this board a lot that I don't necessarily agree with. You don't need to become pen pals with these guys. Calling every week to play catchup is a bit silly to me, especially as the season dwindles down. They're either trying to get you to their school or they're not. So when having these weekly calls, they better be about getting him on campus for a visit or they're pretty much pointless. The coach likes his talent or he wouldn't have set up the call, after a preliminary conversation or so get the wheels turning towards an offer.