As for the new Gold Card application, you WANT to apply for this as a new account - that way you can get whatever rewards benefits you're entitled to for a 'new' account. Existing accounts 'upgrading' aren't usually eligible for the rewards bonuses.
Also, check out the card you want to make sure the reward is exactly what you want. There are MANY MANY cards with bonuses - be sure you're applying for the one with the highest bonus in your desired area (airfare, hotel, general/Chase Rewards, etc). Look over one of the many internet lists of 'cards to sign up for', and look over their signup bonuses. One site I like is
THIS ONE.
1. You'll get approved. If not, call the 'reconsideration line' for the card you're applying for, and speak to a *person* to explain your situation
2. This really won't help.
3. Yes. Keep the green card (unless there's an annual fee), and keep a zero balance. Closing cards does affect your credit score, but it may not be something you care about - not sure of your situation re: credit score.
4. Yes. Apply for both in two different browsers (i.e. 'Chrome', and 'Firefox'). Hit the <Apply> button at the same time for both. Some say this doesn't matter, but it's worked for me, so I still do it.
Most of all - best of luck!