Congrats to your son on his strong profile!
As he is quite likely to be a National Merit Finalist, I would definitely check out this link.
Below are some schools that I think are highly likely to hit the budget (with more details/rationale in this post):
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Mississippi State: Probably around $9k first year and $17k/year subsequently
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U. of Kansas: Probably around $21k
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U. of New Mexico: Probably around $15k
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New Mexico State: About $3k first and $7k/year subsequently
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Oklahoma State: Nearly a full ride
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U. of Houston: About $11k
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U. of Idaho: Full ride
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U. of Nebraska - Lincoln: About $14k
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U. of Oklahoma: About $9k first year and then about $15k
 
Also, I believe Washington State gives free tuition to NMF students.
This post also shared some schools where he could try and get some big scholarships (full tuition or full rides):
- U. of Miami
 - Villanova
 - Wake Forest
 - Tulane
 - Boston U.
 - Duke
 - U. of Notre Dame