1) Drinking alcohol is not condemned by the Old or New Testament (John 2:1-11; Ecc 9:7; Ps. 104:15), but drunkenness and alcoholism are (Is. 5:11; Rom. 14:21). The moral law (like the 10 Commandments) is still relevant, but the ceremonial law, such as abstaining from pork, shellfish, men cutting their beards, etc are no longer observed because the ceremonial law was fulfilled by Christ's death (Rom 10:4; Mat. 5:17).
First, God is the sovereign creator and ruler of the universe. Its his universe, and his rules (Ps. 115:3, 103:19). We do absolutely nothing to gain God's grace and mercy. Or, as the Puritan minister Jonathan Edwards once said, "we contribute nothing to our own salvation except the sin that made it necessary"(1 Cor. 15:10; Rom. 3:20-24) If we believe in God and keep his commandments, it is because God has willed us to be his faithful servants (Prov. 21:1). God created the universe so he could be glorified. He glorifies himself by creating humans who know and love him, and he glorifies himself by creating humans that he will send to hell. (Rom. 9:19,20; Eph. 1:11; Prov. 16:4). The former are known by virtue, faith, and good deeds (Matthew 7:15-20), the latter are known by their wickedness (Rev. 21:8; Matth. 25:46).
Yes, they will go to hell. Almost all humans go to hell (Matth. 7:14). God punishes not only those who are disobedient to him and his commandments, but their entire progeny down to the 3rd and 4th generation (Ex. 34:6,7) and blesses down to the thousandth generation those who obey and keep his commandments (Gen. 22:18). Those who are not servants of God and do not maintain his commandments or revealed word are hell-bound rebels and vessels made for destruction.
5 and 6. Again, God is the sovereign creator and ruler of the universe which includes light and dark, good and evil. He controls the hearts of men, the hearts of the rulers of men, and holds the breath of life in his hand. He is the Alpha and Omega and knows all the consequences of his creation. He didn't set the universe like one sets a clock and then just let it go and sometimes intervenes. He created and actively engages in this world and nothing happens without God.
Agnostics don't have faith, which is an indication of God's grace. Those without God's grace of salvation are damned. And it is possible to engage in forms of morality and righteousness without being moral or righteous in the eyes of God (2Tim. 3:5).
Humans are totally depraved and naturally predisposed to sin and offense against God (Gen 6:5; Eph. 2:3; Rom. 3:23). God gives some of us the grace of repentance and Christ died for all of the sins of those who repent.