You can date anyone you like.
It's highly possible, and within the law. The closest relative you can date is the third cousin, I believe
Your 4th cousin
4th gen
then ur dad would be your cousin as well whether its 2nd 3rd 4th etc depends on how close of a cousin he is to your mom
they are ranked as 1st cousin, 2nd cousin, 3rd cousin. 4th cousin, etc. Also as 1st cousin once removed, twice reoved, three times removed, etc. And then on to 2nd cousin once removed, etc, etc,
4th cousin
4th cousin
His 4th cousin is joe.
I will assume you are talking about July 4th 2011. If so, it makes your conception date roughly October 10th 2010. However, this date could be wrong by a couple of days. It depends on when you actually ovulated.
A third cousin is just that, a third cousin, there is no other name for the relationship.
Your first cousin's daughter is your first cousin, once removed. I some jurisdictions, such a marriage would be permitted and in others forbidden. But, in any case, it might put stress on you family bonds (for lack of better words). If it doesn't work out your relationship with your cousin might not ever be the same.