Mom Needing Help...

So this is going to be kind of long, I'll make it as short as I can I'm just not really sure what I'm asking. ha ha! My darling almost 4 year old son is my life. He's brilliant and funny and amazing to say the least. I love him so much. I am having a hard time when it comes to disciplining him. I understand that all 4 year olds go through phases and he's just learning as I am. I've never had a 4 year old. He's my oldest and its been quite the ride. I look forward to what's ahead for all of us I really do. I love being a mom!
I think he may be "gifted". I've done some research on the subject and he fits most of what a gifted child is. I'm wondering if this has to do with why I don't feel like the discipline, no matter which route we take, is getting through to him. I just feel like I'm not in control. He doesn't get what he wants. I never give in to his demands. We just argue, a LOT! And its ridiculous. I've called him my little negotiator/lawyer many times. He argues everything and he yells and hits (not me, but the walls and couches and not hard). He has the biggest attitude I've ever seen. I'm in amazement one moment, laughing the next, and just not knowing what to do the next.
He also cries at the drop of a dime. The worst example is when we're leaving family members homes and he doesn't want to. I can give him warning after warning. "We'll be leaving in 20 minutes, 10 minutes, five minutes, time to pick up and say goodbye" it does nothing. He cries and not a whimper cry or pouting cry, like he just fallen ten feet off of a building on to concrete. His cousin takes something away. HE hits his cousin. A fly flies by him... All the same crying its extensive and getting a little embarrassing to be honest. We've told him that all he has to do is talk to us about what is going on. But his first reaction is to just cry like that. Its getting old and fast. He absolutely loves to be with his cousins playing. We've even made it so we're all leaving at the same time and all he does is cry like he's hurt. Sometimes he won't even talk to us he'll just cry like that so we are left to guess what happened. Time outs just don't work. I put him on them though because it takes him away from what is happening and calms him down. He gets 3 minutes and when he yells or refuses he gets another minute added on. He is sorry, apologetic and promises it won't happen again after a hug and a kiss. And we're right back to an attitude the next time something doesn't go his way. I wondered about the "gifted" thing because maybe there is something out there that works better for gifted children.
He's not an impossible child by any means and like I said I know that kids go through phases and stages and maybe this is just a long one?? I don't know. I just want some advice, on how to help with the crying. I feel like that is his way of getting attention but he IS NOT attention starved. I have to point that out. He's loved just as much as his little sister and if I think about it, probably gets a little more attention than her. Maybe some comfort in knowing that I'm not the only one who goes through this?? Some suggestions on discipline with gifted children. Anything. Nothing in our house is changing or has significantly in the past few months. I'm just at a loss and in need of some friendly advice. Thanks Mama's!

** I don't want to sound entirely like him may/may not being "gifted" is by any way, an excuse. I just feel like we've tried everything and nothing seems to work. Maybe I shouldn't have even written that. I didn't want to get in to why I think he may be gifted. I just wondered if there were parents of other children who may be gifted that have dealt with discipline problems. I too believe that all children are gifted in their own way. He's not a horrible child as to where I'd have to take everything but his bed out of his room. I just came here looking for some helpful, friendly ideas. Thanks!