If I leave do you think he would understand?

I love my fiance dont get me wrong but ever since we got engaged things have gone down hill i feel like im repeating myself over and over how I want more time with him and its not just that, he says he is going to do something and dosent do it. like smoking he says after every pack he will quit. i know how hard it is i was a smoker too, but really? or like his game WoW I bought him the new one for his birthday because I know he loves that game he promised he would play but still make time for me and our daughter. he didnt and i had to nag him forever and finally the other day he said he was going to just cancel his account so he isnt tempted to play instead of spend time with us. i mean he literally stay on all day until im bitching and screaming at him to get off. and other things simple things... like getting a 5 gallon jug of water here it is 3 weeks later and still no water. but if i do it he will get mad because "he said he would do it" and im impatient. or like how he has been saying for the past week he is going to apply at intel because his job now isnt paying enough, he has been telling me this everyda for the past week... still hasnt done it. and yseterday when i got up what was he doing instead of applying for that job? playing WoW. after he made a huge fuss of canceling his account. i called him out on it and he told me to stop talking so yea i got pissed and left the room he came after me saying thats not what i meant, what i meant was why cant you have a normal conversation with me about random stuff?? i said really? when i do you ignore me. and all he ever says is sorry im really tired of hearing sorry. and like the other day i told he we should start saving a dollar here and there towards our wedding BIG mistake he got all pissed off saying how he needs his money to put gas in th cars. but then he says he loves me and wants to marry me... ughhhh... he might love me but what the hell?? im ready to pack mine and my daughters stuff leaving him a note how i feel and leaving. but i do plan on coming back i just wont tell him that I just want him to know he is either going to take **** serious and do what he says or im gone and next time it will be for good. if he cant hold to the little things he claims he will do why should i believe he wont cheat on me one day? or lie to me?