Six.
If you want to double the force, you need to double either v or B. Changing the angle does not give totally predictable results. The formula is
F = q*v*B Sin(theta) altering theta isn't linear. Doubling B is. The answer is A
Seven
Seven is correct. The poles on a magnet is where the field is the strongest.
Eight
I can't really answer this question. Much depends on where you are and whether or not the readings are true or erratic. It is taking only one parameter into account where in reality there are many. My guess would be that as you move up the longitude the angle increases. So the answer would be near but not at the north pole. Seek out your notes for confirmation.