Agree with those that say you are over thinking things! Just relax it will get better with more experience. Just like anything worth doing in life the more you do it the better you will get at it. Also it is not just about intercoarse. There are many things you can do to get her off without penetration. Keep working on your oral skills. Do it long and learn to do it well and how long it takes you to cum is not going to matter a whole lot anymore.
I always find I last a lot longer with a couple of drinks. Don't know if this is works for everyone though. I find a condom definately softens my erection a bit but not so much as to render it unusable. It seems to be unusual for the first time not to be as you have described, although for me it was the opposite, I was going at it for hours but couldn't ejaculate. As embarassing as I found it, my partner was overjoyed that I managed to last so long, so much so, she didn't believe it was my first time.