1. Your work experience is long enough, and if you all stay in the same company, that will be great. It is better than switching 3~4 jobs in only 4 years, becasue I have to say, with this kind of path, even you get into top b-school, you will have hard time finding your post-MBA job. Schools may consider your high GMAT or your abundant extracurriculars, but the recruiters won't give it any credit. Your past W/E and your expertise are the key points. So, for this part, all you have to do is make a reasonable career path and show to the school.
2. GMAT. Try your best to get 700+. Schools always say that they do not have any preference for GMAT score, do you believe this?
3. If you want to apply for UCB, maybe score 260~270 in TOEFL will be much safer to ensure that you won't be out of the game too soon.