I can understand how anxious you must be.Have you had him checked at the vets for worms,teeth issues etc. to see if there could be a medical reason? When my new pup wouldn't eat I went through the same process as you,but someone told me to wet the kibble with warm water or broth,which brings out the smell.This worked for a bit for me and then we found Royal Canin,which she will eat and also raw chicken necks, a little cooked chicken and little bits of cooked liver.She is still picky,but will eat now.If he doesn't eat much,it is important that what he does eat is good quality.I leave kibble down all day for her to help herself and feed other things in the evening.She will also eat kibble on long walks as rewards.
My Holly eats better if I feed her with the cat,as he provides a bit of competition. Hope this helps.