I think he also merits merit awards 
He has talent in music, talent in academics, and interesting EC’s. Clearly he is appreciated by his schools. Sounds like he has some great choices.
I don’t think it has to be so complicated. I think you can communicate with the schools whose aid you would love to see increase (financial aid and/or department contact, or both, depending). IF it is his first choice, you can say it is his first choice but finances are an issue and is there any way to increase the funding by x amount.
In the course of the conversation the offers from other schools may come up but personally I would not start with that. I would just be straightforward and say it is a matter of affordability and you don’t want him to say no based on money if there is any chance it can improve.
I have seen all the posts about this and it IS confusing and some people on the journey thread were trying to clarify financial versus merit appeals.
I will be honest. My daughter- and I- were more uncomfortable with asking for more based on merit. It just felt uncomfortable to her (and me) asking for something based on talent. We were shy. However, in discussing choices with one school we did say that affordability was a factor and they offered more.
Financial aid appeals were easier because my husband had had a stroke and cost is based on the previous year and we were looking at a tough year ahead. Even with that, some schools stayed with the formula based on previous, prestroke income and some didn’t so that is where we got the idea of inflexibility!
So what I am saying is perhaps you can simplify this by figuring out a number that would work for your family, rather than trying to match certain schools, apples, oranges and peaches It feels less like Vegas, right? Just straightforward. “This is his first choice, he got some offers at other schools that make them affordable, cost is a factor, he would like to choose your school, is there anything we can do?” You can also ask about work study and other ways your son could take on some responsibility.
There are others who know a lot about this. We were shy about it but also increases of even $20k weren’t going to help us out so we didn’t do it. My music kid has done great regardless
Good luck to your talented son and his supportive parent!!