#1, yes. In fact, 996 Turbo adn GT3 motors have a 964/993 engine block. 996 also had to be built to a price. Porsche couldn't afford to build them like they used to. M96 based motor is known for some "teething" issues.
#2, yes. Value in both "last of the aircooled" and also due to smaller production run among other things.
#3, what the 993 owner overlooked is that the 996 has superior performance
