He could acquire in-state status at U of Utah after the first year. Most states do not permit this unless the entire family relocates, but Utah does. They also give decent merit for stats like your son’s. STEM programs are strong so it could be a good safety.
Have you looked at Olin College of Engineering? It’s a tiny school, project-based, and very prestigious; and they give half-tuition merit to all accepted students, which puts the maximum cost at around $54K/year. This is double your “safety budget” but Olin is not a safety school; it’s comparable in reputation to other schools you’re contemplating paying much more for. Electrical & Computer Engineering is one of the three degree programs they offer.
The Cooper Union in NYC is another small but top-notch STEM school with automatic half-tuition merit for all. Total cost of attendance with on-campus housing is 46K/year.