The first one I don't know as I do not have a store. Do you pay for a store?
The second point about listings staying up after being sold I can answer. The GTC's( Good Till Cancelled) listings which we all use for our fixed price listings will stay where they were even after being sold. Buyers cannot see them, only the seller, so if you are truly out of stock just end the listing. If you plan on getting more stock in you can leave it up but it will count towards your monthly allowence when it comes time to re-list.
The real advantage to leaving it up, is that the sales will keep adding up. Example, if you had 10, sold them all, then added 10 more the listing would show that you had 20, sold 10 =50% sold, then changing until you sold them all. Showing "only 1 or 2 left" can help sell the last ones.
You asked about the watchers earlier, Tyler mentioned there were reasons why some listings did show when there were 5 or more, which he went into detail about. He also said it depended on popularity, and other factors. Watchers can be your competition, folks who like the item but can't afford it, or maybe they like some of your other items and are using it to get back to your listings quickly, who knows?
I did look at your listings and was surprised at the Tang one being free delivery, an almost 5lb item through CP will cost as much, if not more than your selling price. Also selling one video game by itself, is not considered a bundle. Other then that good luck selling on ebay.