1/ Vega is sensitivity of option price to change in level of implied volatility. Appraised is an unusual word choice.
You'll have more gamma if the asset price is near the strike price of the option. But gamma can actually be lower near expiration for the same strike if its fairly out of the money - gamma will only be higher for at/near the money options.
6/ Market makers buy and sell volatility and outside of retail, prices are usually quoted in vol terms. That's not to say that professionals can't do some crazy things trying to hedge risk, including theta (time) and rho (interest rates) but the original trade is a vol trade first and foremost.
My slightly different explanation: Delta is the 1st deriv change in price of the option wrt the value of the underlying asset. Gamma is the 2nd deriv, ie the rate of change of delta. As expiration approaches, gamma gets very like a dirac delta function, centered at the strike price. Easy to understand - moments before expiration a call option value is either worthless or exactly (Underlying - Strike price) Thus a delta of either 0 or 1 (-1 if you are short) with gamma equal to delta.
As the original poster explained, traders hedge by buying or selling the delta amount of the underlying (if delta is 0.5, you do 50% of your notional contract size). As the underlying moves, the short trader needs to buy when the underlying rises (his negative delta is increasing) or sell when it falls (his delta is decreasing so less hedge needed) to maintain a 'neutral' position wrt to small changes in the price of the underlying.
Recall, gamma is the rate of change of the delta and so determines how much the hedge needs to change. On day of expiration at the money strikes have very high gamma and thus subject the short option trader to large whipsaw risk - the need to add or remove a hedge aproaching 100% while chasing the underlying. The art is really in deciding when to hedge on/hedge off and how much, regardless of the formulaic delta and gamma values at the current underlying price.