MDon:
Those are great schools you are interested in attending. My son is also a 2011, who has pretty much always targeted D3 for a variety of reasons. I can offer you some info based on his experiences thus far. Ken is right - it boils down to acceptance to the school. The coach will decide he likes you, then he's got to make sure you meet admission requirements. Then, he's going to work harder to get you interested in applying, then, when you are accepted (unless you decide to apply early decision) I'll assume he needs to work harder to get you to select their school, send in your deposit, and attend. Unless you apply binding early decision, it will be a long "courtship" as has been described to us.
You asked about how to gauge interest - Here are some things that my son has noticed from the D3 coaches who have the strongest interest, who in turn are the top choices for my son - its a two way street:
1) they were the coaches who have seen him play in person, in game situations, usually at a showcase. (video is a great tool to get their attention, but it seems "in-person" is what really kicks it into gear.
2) they are the coaches proactively seeking him out, checking in with him on his cell phone (kind of an obvious one)
3) they have actively requested unofficial transcripts, current class schedules, test scores, etc and vetted that data with admissions.
4) they have proactively worked the hardest to get my son out for overnight campus visits, and have arranged the meetings/interviews with admissions, etc.
Once they liked my son as a player and person, it all seems to then focus on admissions and getting him to experience the school culture and atmosphere.
Once again - best of luck to you.