I don’t see why he wouldn’t get a waiver if the doctor documented the reason for the SBO and also no complications like issues with bowel movements or nutritional deficiency.
The cause for the bowel resection(Meckel’s diverticulum) isn’t DQ like it would be for inflammatory bowel disease.
The USN Manual of Medicine (MANMED) says Meckel’s, if surgically corrected more than 6 months ago, is not DQ so you should be clear time wise.
The concerns with small bowel resection are chronic abdominal pain in the future due to adhesions and nutritional deficiency (could cause anemia).
Just out of curiosity, did your son have blood work done as part of the DODMERB exam?