I went to post on your thread but it looks like it locked up. So I'll say it here - you get my support for giving it another chance. I may get beat up here but I am a firm believer that when someone strays (only once that is) it is a reflection on ourself as much as on them and we need to realize that we weren't giving something.
They shouldn't have done it and should have communicated to let us know something was wrong before they reach that point but sometimes they don't. This is called a mistake.
Are you at a point that you think you have a good idea where you can improve the relationship? Are you convinced that he has a good idea what he needs to do to improve the realtionship? Are you both committed to putting in the effort to make it work?
Make a list of all the great qualities this person offers and all the bad qualities he offers. Then make the same list for the next person you are going to date. Then put down the odds you think this person will do it to you again. How remorseful is he that he did this and hurt you? Then put down the odds that that future person will stray on you (that's estimated to be 60% of guys do it)
What you should end up with if you are even considering this is one person that has lots of qualities that you love and confident he will not do it again because you have corrected the problems and he is better suited to tell you there is a problme before it reaches an affair AND another fictional person that is a complete crap shoot who has a 60% chance of an affair because they haven't gone through the leaning curve. (this one may be better or may be worse).
You are young! If you gave it a year to see if the work can be done to make your realtionship better and be back with the person you choose the first time isn't it worth the shot? I say year because I would think that is about the time it takes to put everything behind you and get to a great realtionship. Of course you'll know before if you are on the right track or if things aren't getting any better
If you feel secure he won't hurt you again and his good qualities outweigh the bad. I support you trying, just know that it will be your turn to say no thanks if it isn't working.
