In Oedipus Rex, is Oedipus' fate sealed from the start? I need help understanding the question more. Here is some background on the rest of my...

Judging by your
synopsis, you have a good understanding of what the question is asking. However, you are also
right in believing that there is more to this question than a simple consideration of whether or
notis responsible for creating his fate (and if so, to what degree is he
responsible). 

To be clear, the question has three parts. 

• Part one asks, what events or outcomes in the play can be directly
  attributed to Oedipus? One of these would be the falling out he has with his brother-in-law,
  . 
• Part two asks, what events of the play are outside of Oedipus influence
  or control? The prophecy handed down in his childhood was outside of his control and it is this
  prophecy that propels Oedipus into action and toward doom. 
• Part three
  asks, which of these dynamics seems to be the stronger force in determining the action of the
  play (and is Oedipus really responsible for any events in the play if his fate is already
  determined)? 

One way to narrow this whole question down is to
look at some particular instances. Oedipus kills his father on the road. Does he do this because
it is part of his character to be proud and unyielding? If he were a different type of man,
would he have simply gotten out of the way and let the other man pass? Is this murder directly
attributable to Oedipus' attitude/personality?

Or, was Oedipus forced to act
this way because fate and the gods had put him in conflict with this man on the road (who
happened to be his father), thereby creating a situation where a person like Oedipus would act
in a predictable and violent manner? 

After all, Oedipus is fleeing his fate.
This is his intent. The only reason he encounters his father on the road is because he does not
want to kill him. We might say that Sophecles presents us with thisto suggest that Oedipus'
situation on the road is either extremely bad luck or is created by the gods, by his fate, and
outside of his control. 

Indeed, in the end, Oedipus feels that he had no
control over the outcome of his life and that this becomes especially true because of his
efforts to avoid his fate. Though he is not responsible for the prophecy that set his path, he
is the person who carried out all the deeds for which he punishes himself with
blindness:

"Oedipus, damned in his birth, in his
marriage damned, / Damned in the blood he shed with his own hand!"