Um.
Apparently you are not the only one confused.
"Blood Oaths" is not a stand-alone plot: It hangs between two events in two stories about Nick and Jeremy: the first one, "Dupree's Choice" in which he talks about his estrangement from his family in very sketchy terms. The second is in "Home for the Holidays" in which Jeremy guides Nick back to Elk Mountain. "Blood Oaths" takes place a week before Christmas, in preparation for Jeremy's reintroduction to his family and the discovery that his parents are no longer in Elk Mountain - the house has been all but abandoned, and his sister encourages him to phone his mother.
There are points in this plot that are not clear: however, they will be made clear in another story!
What "The End" means is the end of this episode, this short story.
And in answer to your very good questions: their blood oath went two ways: it was the promise Jeremy made to keep the rape secret from everyone at Sue's insistence. The second was the secret Sue keeps of Jeremy's, which was only vaguely hinted, but concluded in the comment that he wasn't going to be making any grandchildren.
It was Steve's house they were at in the flashback - I should probably make the sentence structure a little clearer. Steve's mother found them, to her puzzlement, wrestling in bed, but didn't think much of it. Well, at least not right away!
Yes, more plot is in the offing.