Congrats on your son’s accomplishments; he sounds terrific. If you haven’t found this already, here’s a thread that describes the schools that offer big merit for National Merit: Big merit NMF/NMSF schools and their specialties
An in-state school as strong as UIUC as a “likely” sets a high bar for the rest of the list. We also were in the situation where we were full pay, but not so wealthy that tuition costs didn’t matter. So for us, we took flagships that weren’t in-state (or in tuition reciprocity states) off our list. Our S22 ended up at one of the “big merit for NMF” schools listed above and is very happy. It was a better fit for him than our flagship.
I do agree with the idea of going ME rather than Aerospace. A student can always do an Aerospace minor or concentration, or target their internships to aerospace.
For your current list, I predict he will get into all his safeties and targets. I predict he won’t get into his reaches, just because admit rates are so very low that these schools are unlikely for any applicant except those who have won specific prestigious national awards. That said, he certainly is qualified academically for these schools, so no reason not to apply and see if luck goes his way.
Best wishes!