Regarding the e-mail silence, my 2017 had a very similar experience as the OP right after attending HF last Summer. We learned a lot from it, and while each kid's experience can be different, we saw some common themes from the 10+ schools (mostly D2/D3/NAIA) who engaged my son:
1. That first e-mail is sincere; they are not sending it to every kid at HF. But if they are a D1, they are down to the last few spots open and casting a wider net, and if they are a D3, they are really just beginning to fill their roster and will cast a very wide net to find out who might really be interested in their school and program. It is not unethical or shady--it is part of the process of getting the best players interested in their programs and improving their chances of landing some.
2. Your son's reply e-mail has to be very specific showing evidence of interest in that school. Addressed to the coach by name, specific to the prior contact, indicate why your son is interested in the school (i.e. major offered at the school) and baseball program, and shows some indication of a future campus visit to meet all of the coaches and tour the campus. If there are mistakes or it sounds generic, coaches will end it there. One coach told us he eliminates almost one-half of his candidates just from the way the player responds in the e-mails they send him.
3. The academic schools want the test scores and transcripts immediately via e-mail. It can go silent after you send them for two reasons: (a) it can take a little time to get somebody in the Admissions department to read and assess them, and (b) Admissions tells the coach getting the kid in is in doubt. Coaches at academics need certainty of admission before they will really be interested in a player no matter how much they like what they saw on the field.
4. By far the most effective e-mail response reads my son got were the ones he sent to the coach with the Subj.: "Name, Position, Possible Campus Visit Date of XX, XX-XX" As soon as he showed a sincere interest in the school by committing to a campus visit, the response back was very positive. Some offered to have him watch Fall practice or scrimmage. Some had school specific "student days" to tour campus and then the coach would walk him around. The sooner you narrow down choices and focus on visits, the better your progress will be. You need to show your interest is sincere before they will show sincere interest. And if the Head Coach is not there to spend time with you on the visit, drop the school immediately.
5. Once the campus visits happened, the e-mails ended and all communication was between the coach and my son, by text and by phone call. As much as it drove me crazy to not know every word that was said, that is how it worked with every coach. The coaches already met me on the visit--it was now between him and my son. I gradually accepted that was the way it was going to be. All the way to the very end when he was finally told he had a spot on the team, which happened very late for my son, I was not a part of the process or discussion. Fortunately my son communicates very well with adults, and I was confident I could trust him to do everything the right way. No doubt the coaches use that as a big part of their final evaluation process.
As others have said, don't be too alarmed yet by a non-response in mid-August. But be sure to follow up quickly and then reach out with the Fall visit interest and see if that revives the process. Applications start in October for most schools so that is when your son really needs to know where his most serious opportunities are.