I wish I would have found your sitch sooner I am 27 myself so understand some of what you feel. Here are some thoughts.
Ok so I bet that most of your friends and relatives and even your mc (shame on her!) are telling you that you are young and that you have your whole life ahead of you and blah blah blah. I hear this all the time too, and I think it's sad. Its indicative of society's willingness to throw things away when they get too hard, and our inability to find happiness and fix what we do have.
Only you can decide if your M is worth fighting for. I had to make this decision for myself despite all the people that think I'm young enough to find someone better. This notion that only older marriages are worth saving is illogical since surviving a young marriage is necessary to have an older marriage. Does that make sense? Additionally I also believe that our generation is poorly equipped to handle the rigors of marriage. In an age of disposable cOnsumer goods it is no surprise many young people treat their relationships as disposable. Kudos to you for rising above that.
Now all that being said you have your work cut out for you. As you have mentioned you have a lot of bad traits to work on. I suggest you seriously put a lot of effort into these traits, because no matter what the traits you have now you WILL carry them over into your next relationship. Whether that R is with your H or someone else. That means that you might as well fix them now, or risk messing up your next R. I'm sure you don't want that.
That's why the key to DB is self improvement above all else. If he decides not to reap the benefits someone else will. If you don't fix yourself you'll just hurt your chances in your next R.
Now about that counselor, she saw some pretty stubborn traits in both of you and rather than help you both become better people she said it would be better to just end it. How ridiculous! Would you trust a watch repairman if you took a family heirloom watch, and he said you'd be better of just tossing it and buying a digital watch? You went in for her to facilitate the healing process not to speed up a D. You can destroy your M for free.....
Keep doing your 180's not for him but for you. You deserve to have a stress free relationship, if you don't get over these hang ups you will just make yourself miserable.
Let me tell you from a guys perspective if you don't fix the nagging and jealousy, you will scare away the next guy. No guy likes it when his girl takes out the anger she has for her ex on him. It's just not fair.
That being said if you will put all that effort in fixing yourself might as well fix your marriage too. See the logic?
1. Fix yourself 2. Fix the marriage 3. If the M does not get fixed, fix yourself to ensure you don't ruin the next R before it even starts.