Your son appears to be having hypersensitive responses to texture. How long have you been trying more textured food? Gagging is a protective reflex. But, it and vomiting is not a pleasant experience. Children can quickly decide that food is no fun and even adversive. This can create feeding problems for years to come.
Gagging and vomiting with food can indicate a variety of feeding issues. It is possible that he just needs texture introduced gradually for a while longer. I suspect this will be difficult since he is now rejecting textured food. He could also be suffering from several other problems including reflux or even difficulties related to his swallow mechanism (not likely, but possible).
Children need pleasant experiences with eating or they learn that eating should be avoided. This is my biggest concern for your child. Also, eating textured food is an important link for oral motor skills that are the foundation for development of speech skills.
As a speech therapist who works with children with feeding difficulties, I recommend that he be seen for a feeding evaluation by a occupational or speech therapist. They will be able to help you plan an approach that will give you peace of mind and move your little one forward on developmental feeding skills.