my dog used to be pretty bad. we did a leave it exercise in which we fought him to leave the food and sit down every time I walked up to him and gave him a treat when he did (usually something special, also clicking as soon as he moved away from the bowl). after he got that down without looking nervous, I started to put my hand near the bowl with a treat and clicking when he went to take it. after about 6-7 months (yes months) I started to sit next to him and pet him a bit while eating and treating him the whole time, now he is very good, we still do it every day (both the leave it and the petting+treat combo) now the only look he gives me is when he's looking for a treat. :3 (my dog was far worse then yours, he would start to growl at about 2 feet away and give the warning signs to strangers from like 5 feet)