How to deal with a defiant 6 year old?

i have a 6yo boy. im not sure what to do. hes just defiant. unsure if im just over thinking on this and its normal or if it isnt. homework is a joke. he tells me he wont do it and i fight him for hours on it. he says he doesnt know how too do it when he does. like writing his name. he says he doesnt know how to write it at the top of his work. i know its intentional because before ive said ok do it and u can have a candy bar and he did it. but im sorry i refuse to bribe to get him to do what he should be doing anyway. asking him to clean up is a joke. he outright says no. ive even tried throwing away what is left out of place. didnt work. next time he offered to help put them in the trash. he wont eat then he wants chips and stuff 20min after the meal. i tell him no u dont eat and u dont get snacks and he says im abusing him by doing it. i used to spank him but he started telling people we "hit him" and i was scared people would think he was being hit inappropriately which he wasnt. a firm smack on the butt in my opinion is not abuse although i know some think it is. time out corner did no good. im at a loss here. i just want him to be a well rounded well behaved happy little boy.