Start very small, 3 steps of focused heel, then "good" and treat, then 5 steps, 3 steps, 2 steps, 5 steps. Always stop and "good" and treat.
Don't treat whilst walking as he needs to drop his head to eat the treat and as such you are teaching him that it is ok to look away whilst in a focused heel which you don't want.
When he gets better at it then increase the steps before giving a treat.
To stop the snatching play a game with him... hold a treat in your hand, every time he tries to grab it say "uh-uh" and move the treat away... when he eventually stops trying to snatch the treat, say "good" and give it to him. Play this often.
Another game that is good for helping with heeling is the "touch" game. Have a treat in your right hand, hold out your left hand, get him to touch it with his nose, then good and treat from the left hand. Once he has the hang of it start saying "touch" and then you'll be saying "touch" and he'll be spinning to find your hand. Its great fun... hand high, hand low, hand behind your back... whereever "touch" and he'll find it for that treat that is in your other hand. When doing "heel" have your left hand by your waist.. say "touch" and he'll keep by your side and touch that left hand and then you "good" and treat from the right.
I haven't been using his treats while walking anymore as I was suggested the hot dog/sausage, which has worked and he can nibble away at it while walking but the thing is he's so rough with it instead of just nibbling away he's catching my skin over and over and I can only take so much of those razors.
The idea of not grabbing my hand he gets, well atleast only when I'm hand-feeding him his meal. I usually take a fist full of his kibble and hold it out to him and he licks at it at times but just immediately backs his head away from my hand and waits, I click and release his kibble and he eats it right out of my hand with no problems whatsoever.
I've also have started teaching him touch because I felt like that's the only other way I'm gonna be able to teach him to heel without having to have my hand cut up by his razors, he probably touches my hand with his mouth closed probably 1/10 times right now but we're working on it.
I taught my dog to follow the food and play the touch game that KaiserAus mentioned above, before I ever tried using it to assist in a heel. Sounds like your dog is food motivated. I would just take a couple steps back and work on luring .getting the pup to follow the food, Make the pup think a little. Then you can add sits, and downs with the food. Reward a lot. then eventually work it into the heeling.
Yeah I've started teaching him touch for targeting since as I mentioned above I thought it'd be the only real way of me teaching him to heel. He definitely is food motivated, but ever since he was 8 weeks luring just hasn't worked with him and I read that some puppies just don't do it naturally and rather offer behaviours and vice versa. Is this true? Because as it is, he'll just try offering behaviours like sit, down, adjusting his position and speak to try and figure out what's going to get him the reward.