Help! My Puppy is Not Chewing his Food

[Sherman'sMom]

I have gone full circle with my Brittany spaniel since I got him. I started raw in the evening and no grain high protein kibble in the morning (in hopes to free feed throughout the day, like that's possible with my glutton). I went to a store bought raw (pets 4 life) and struggled for the past month or so to get him to eat the food. I tried every flavor, tried switching meals around and gave up and started making my own raw again.
I'm not sure if it is because the store bought stuff was just mush but he is not chewing his food. He has always gotten chicken necks as a treat (usually frozen) more recently he has started to chew them less and swallow them almost whole. I figure I may have to stop giving them to him as I am scared they will get stuck in his throat. since he is 7 months old now and I want him to chew for the health of his teeth I started giving him bigger chunks of meat with his supper (I give 70+%meat 10+% bone and an offal/veg mush, sometimes a little plain unsweetened yogurt). First meal like this he licked the mush off the chunks of meat tried chewing a little and gave up looking at me like I was doing something wrong I eventually ended up blending the meat and he ate it.
Last night he had turkey neck for the first time he barely chewed it. but I thought at least he ate it and didn't choke. 4 hours later, while we were reading in bed Sherman threw up. There were giant chunks of whole neck that came up along with pretty much everything else he ate. I'm guessing he threw up the neck because his body couldn't digest the huge chunks of boney meat.
So know I have finished with my novella of background info, does anyone have any ideas how I should continue with this? Should I freeze the neck (this one was semi thawed)? Should I chop his food smaller and gradually get to bigger chunks? Should I just throw him a slab of meat for him to swallow and throw up, cuz I figure he will try to swallow it whole if at all?
I'm getting pretty frustrated, I need help!!
on a side note if I can get this sorted out I plan on quitting the kibble when this bag is done as I was only doing it (against everyone's advice) to free feed him through the day, and since he would devour the entire bag if i offered it, free feeding is out of the question.