I am no expert by any means but I say get him fixed asap and I bet it lessons big time. My Cutty started acting like this around a year or so. I knew something was wrong cuz it just was not him and we have every test xray etc run to make sure he ws ok and he was. Putting my boy on his back only seemed to make him worse, maybe that was just me being the over protective mama but that was a no go for me. He got to the point of scaring me too. Went from loving to be picked up to no more period. Didnt have kids at this time so I dont know if he would have acted like this. BUT he was fine when he wasnt in his mood. Anyhow we got him fixed, hoping it would help bring him back and let me tell you it was like night and day. Seriously! He still isnt the same easy going boy he was before and this is why I will always neuter earlier cuz he changed. BUT he only gets grumbly now for the most part when we have to pick him up to clean him or something. Or if I accidentally step on him or hurt him, he gets mad and will grumble for a good 5 or 10 minutes. lol. BUT he is no longer scary and I know he wouldnt bite me ever now, whereas I wasnt so sure before. He is the best with my daughters and my pug so I do not worry about them at all. I highly suggest you have him neutered. Even if you plan on breeding, you dont wanna be breeding a dog with that attitude ya know? We do have a lot of great members who have tons of knowlege with training, I do not. Maybe there is another way to get around this but for me this is what worked.