Don't try to 'make him happy'... set limits, and be gentle, yet firm. Stay consistent and if it's teething (15 months is prime time for molars), this too shall pass.
If he's throwing food, I'd say he was finished with his meal, reminding him that we don't throw food, and immediately take him somewhere he CAN throw something (ball in yard, bath toy in bathtub, ball in playroom, etc)
If he is hitting, get down on his level, hold his hands by his side, and tell him hands are for hugging, not hitting. A simple 'Hitting Hurts" is really all that is needed at that moment.... simple, direct, firm, but not yelling/screaming. Encourage an apology by helping him say sorry, say it for him, or just mention that we say sorry, then redirect. If it continues, remove him/leave the situation (leave the room, or playdate, etc)
Should you be concerned? Yes... you should be concerned enough (as it seems you are) to reach out and ask how best to handle things, find out what other people do in these situations, and evaluate how you want to handle things as a family. Write down a list of rules for you and your husband to follow, as to how you will handle certain situations.
Read Some books. I'll be glad to offer some suggestions on books for you, or specific scenerios you have. Email me any time.
You're doing a great job.
(they rarely sit still by the way!! haha)
(oh and someone mentioned milk... that is a good thing to try. Other major behavioral food culprits are artificial preservatives and colors.... try using whole foods as much as possible)
Good luck!