However, in response to your questions:
(1b) Since beta is the measures a stock's CHANGES relative to the market,
the stock whose changes were most in line with the market would be the one
whose beta was closest to the market beta. your selection of Mississippi
Power Co (the second one) is correct. Following this logic if a company had
the highest percent of market risk (R-sq), it would not necessarily be most
closely related as regards changes in price. In the absence of Mississippi
Power, Minerals Technologies with beta=1.06 most closely relates to market
changes. However, its R-sq is only .02.
(2) The best forecast of alpha is the estimate of the y-intercept using
least squares regression.