Once ur pup is 2 month old u can gradually decrease his meals from 5 to 4. But dont do it suddenly. Rather replace one meal with treats which u can give him while playing/training. Go down to 3 meals after he is 6mnth old.
U can give one or two RC diet & the rest can be home made ones. Go easy with home made foods so as not to put his stomach in pressure. Try curd, boiled rice, cheese, eggs (occassionally), some veggies like carrots (can be given raw as treats), peas, etc. Avoid chappati & daliya for the time being.
Once he is 3 mnth u should gradually introduce him to meat. Non-veg is good for proper growth of pups.
Change in behaviour can be due to hunger or sudden change in eating pattern. Try playing with him at the time when u used to give him the 5th meal & give some nice treats instead of a whole meal. Give him chew toys to play. Dont encourage bad behaviour by giving attention. Rather ignore him if he barks a lot, tries to bite. Give him meal/treat/attention only after he is calm.
Hope this help.