Son is 3, w/gtube (ftt, global delay, gastroparesis, hypotonia, chronic vomiting) gaining weight some, but height stopped over a year ago. suggestions?

No easy answers: Kids like this who have so many global problems are very difficult to pinpoint why growth is restricted. It could be caloric, even though you say he is gaining weight, due to the chronic vomiting. Could be a metabolic disorder with some type of mitochondrial dysfunction. It could be hormonal, growth hormone affected by chronic poor nutrition. Suggest both pediatric GI and endocrine work together.

Bone age: I would get a bone age which is an x-ray of the and that gives what age the bones appear to be based on the growth plates. If he turns out to be small for his age on the bone age, then i would see an endocrinologist to find out if growth hormone therapy would be appropriate for him.