Keep going back. Perhaps keep a food diary and note of symptoms, and/or a list of incidents as you have mentioned here. They are overstretched and I have found that if you keep going back and are clear and informed, they will help you, specially with children. They are overloaded so sometimes it feels like you have been forgotten. Make sure they don't forget you but always be polite!!
If you feel that the consultant is not helping you can ask to be referred to another consultant.
If you can't get a definite diagnosis now (and this is what happened with my son) then you could suggest a 'gluten challenge' (i.e. retest) could be done when he is a teenager, but keep him gf for now. My son is now almost beyond teenagerdom and lives a gluten free life, his notes just say 'suspected coeliac'. He never had the challenge, completely pointless imho, as he had positive bloods but no biopsy.
On the positive side you know what is wrong and can look after him.
Perhaps ask to be referred to dietician, because he also appears to have dairy problems, and we were told that it's really important for coeliacs to get plenty of calcium. Dieticians get a bad press on here sometimes, because they can't help with the coeliac diet, but they are very good at knowing what nutrients your child is lacking or getting too much of. (They get you to keep a food diary for a few days before the appointment.)
Hope this helps!
(Also you could phone the coeliac UK helpline)