1) Some people use kerosene or base cleaner every time, I don't think it's needed. If you have a brush handy though, I would definitely brush your base to clean it, as it only takes 30sec. Normally I just use soap + water + a paper towel.
2) That scrapper looks gimmicky. Either buy a cheap scrapper from your local shop ~ $5, or do what mingle said, either would work great.
3) I like to wax after every time out, but that's just because I love how my board feels when it's freshly waxed. But on man made snow, I would say at least every other time out would be a good idea; that stuff is harsh.
4) Don't reuse the excess wax, when you heat the wax it's chemical properties become slightly changed, so don't reuse your scrapings.