Question about Ending (Spoilers)

1) I think it's safe to say they had sex. The implications were there and it just made sense.

2) From an interview I read with the director, he said that the film was mostly autobiographical and claimed that relationships can really save people at certain points. He mentioned he might have killed himself had he not had a relationship with someone at a specific time in his life. I think that ties into the Karen plot. I doubt Wilson would have actually killed himself over her, but Vivian was an important (to say the least) rebound for him. Like the director mentioned in the interview, he needed to know that kind of love was still possible. The fact that we aren't told directly, I think, allows us to hope that they will see each other again some day. When that day is, we don't know. All we know as that they both found something they were looking for in each other.