MC,
Encourage your son to call. I have posted many times about this. In Northern CA. there are 9 DI programs. Even if they recruit 10 players each, that is only 90 slots each year. When you consider high school and JC, there are substantially more DI players in Northern CA than slots available.
This, of course, does not even consider that many slots are taken by players outside of Northern CA.
If your son has the fire to play college baseball at the DI level, and this school is "the" fit, he has to be very aggressive in expressing his interest and making sure the coaches know.
From experience, let me suggest the reason he might not be calling isn't that he doesn't want to bother them. Rather, it is his fear they have indeed lost interest or gone a different direction and he does not want to hear that. He feels a bit helpless in how to manage things if that is true.
With your son being a senior and no place to attend and play college ball as of April 1, time is tight.
Personally, unless he knows more about this program than a 4 hour visit, I wonder if it is a good fit. Has he visited the school, met the team, stayed on campus, been to classes? Those are all very important.
From what you described, my bet is that coach said similar things to many players. The important aspect is that coach did not make an offer.
I think your son needs some help and support.
He cannot continue to hold out hope through "they are too busy" thinking.
This is his college choice and baseball experience.
If they have moved on, it will benefit him to know that so he can do the same.
Leaving it like it is does not help him find the right "fit" for college and baseball.
He has plenty of time to explore other options. But this one needs to be ruled in or out and that can only be done by contacting the coaches.
Again, from experience, I would support your supporting him and realizing this is truly hard, but he needs to know the answer and to not guess what whether the coaches are busy and/or not interested. You and your son need to control every aspect you can of a very difficult process.
Hope this helps. Good luck to your son.
You might want to post this in the Recruiting section and get more visibility and responses.
'You don't have to be a great player to play in the major leagues, you've got to be a good one every day.'