First Question: Who did Cain take as his wife when he was cast out of Eden. According to the bible, the sum of the human population consisted of Adam, Eve, Cain, and the (now) deceased Able. Or was god busy making other people not worthy of mentioning?
First, many Christians do not believe in a literal account of Genesis and second the most common beliefi s that Cain married his sister.
Second Question: How many deities do christians really have? Is it one with multiple personalities (god, jesus and the holy spirit) or three separate beings, thus making christians polytheistic?
It is one God in three persons.
Third Question: According to the ten commandments, "Thou shalt have no other gods before me", does this mean that it is acceptable to have other gods after "me", so long as they are not of a higher station?
The way I look at it, why would someone worship a lesser god is they still worship the all-powerful Abrahamic god?
Fourth Question: Again, according to the ten commandments, "Thou shalt not make wrongful use of the name of thy God." Aside from never actually giving a name, what would be a "rightful use" of this un-given name? Generally, it is accepted by christians, that this name is YHWH, transliterated from Hebrew, and means "I am", or in Latin,
Sum.
"God" is essentially the name which Christians call the deity they worship. Thus when taken in this context one shouldn't blaspheme.
Fifth Question: If you accept the omniscience of this god, that is, that said god is "all knowing", then said god must already know the fate of each and every soul before it is incarnated into flesh. If this is so, then how can this same god condemn anyone to hell, having the foreknowledge of what life path that individual will take.
People condemn their own self to hell. People have free will and it is they who use it to sin.
Sixth Question: If, according to the bible, 144,000 are the sum of those so chosen to enter heaven, then are the other 6,754,587,719 people on earth are are just plain out of luck?
Only Jehovas Witnesses really take that number seriously. The traditional view is that it is symbolic.
Seventh Question: Again, according to the bible, in the end times it is said that the dead will be freed from their graves, and from the sea, and judged according to their deeds. Does this mean, at this moment, heaven is empty, and everyone is just waiting around to be judged?
It depends on which branch of Christianity you look at. Paticular Judgement is the belief that souls are are judged when they die and for lack of a better word are "sentenced" on Judgement Day.
Eighth Question: What possible use could god have for gold, and precious gemstone to decorate heaven with and in such abundance?
I don't really understand the question. If this is about passages which refer to gold or other wealth in Heaven then it is surely being figurative.
Ninth Question: If god has a throne, and jesus has a at least a floor-mat to sit off to god's right side, and the twenty-four elders mentioned in revelations also have somewhere to sit, does that mean everyone else has to either stand or fly around all the time? And why would anyone need anywhere to sit anyways?
Again, figureative
Tenth Question: Why would god bother to "prove" his existence to Moses by manifesting first as a flaming bush, then as a pillar of flame, but never bother to make another personal appearance again?
God does make personal appearances to people after appearing to Moses.
~I