A minor point, but "complete his college" sounds funny, so I'll say "complete his education".
For the hypothetical clause, there are two possibilities here. First,
he's either stopping now, or he's still going but has already decided to stop:
If he were to continue college ...
Second, he stopped going to college some time ago:
If he had continued college ...
If he hasn't yet decided whether or not to stop, you should use "If he continues college ..."
For the rest of the sentence, you can't use would have completed, because he hasn't graduated yet. However, English allows the use of the present for the future in this situation. For the first case, you get
If he were to continue college, he would complete his education by 2013.
Perfect.
Let's try the second case:
If he had continued college, he would complete his education by 2013.
This doesn't sound right to me, since I'm so used to "If he had ... he would have ...". Normally, I'd use the progressive in a situation like this.
If he had continued college, he would be completing his education by 2013.
However, I don't like using the progressive form with "by 2013". So let's use the "going to" form of the future with "would":
If he had continued college, he would be going to complete his education by 2013.
The verb form is a little long, but I think this is the best alternative.
Best Answer
The latter seems very wrong to me. Putting the word "not" after "should have" may possibly be correct form in other languages, but seems to me to be incorrect in American English. Also, I'm no English professor; but I would question the use of a comma in that sentence.