where ever they comsume it, the money must go somewhere and finally being invested by someone who wish to, so no worry

Answer for Q1:

In economics consumption is primary motivating force in the wealth or utility maximizing paradigm. Consumers choose the group of goods and services that make them happiest. All activities are directed towards consumption, either of traditional goods and services, or of personal and perhaps unique activities. (See Irving Fisher's Rate of Interest)

In a one-person world, production is directed towards those goods and services that the individual perfers. With the advent of exchange, consumption is altered by the ability of individuals to take advantage of the gains from trade to adjust their consumption activities with others in the economy.

In Keysenian consumption is the total personal consumption expenditure, or the purchase of currently produced goods and services out of income, out of savings (net worth), or from borrowed funds. It refers to that part of disposable income (income after taxes paid and payments received) that does not go to saving.