Patronous and Lily and World Domination- oh, my!
Okay, first things first (and I may be behind the times here):
I really don't think Voldemort would have sexual relations with anyone. The only reason I could see would be for toture, but a Crucio works as well. Unless he wanted something more henious then that, as rape pretty much is....
As for a Patronous, riddle (pardon the pun) me this- what would the dementors suck from him? Since none of his happy memories would be the sort of thing they would want to take away... would he need a Patronous?
And on the topic of him taking over the world. Of course he would of, I'm sure, but after he had completely destroyed England and Harry. Also, it takes some time to get around. As of DH, he's really only been back in a body for 3.5 years. Grindelwald never made it out of Germany/eastern Europe, and people in England have heard of him. Imagine how much everyone around the world fears Voldemort. Compare how Americans felt about Hitler/Saddam Hussien. Plus, in Potterwatch, they mentioned Voldemort sightings abroad (when he was looking for the Deathstick). So he moves around a bit.
Of course, you do have a fair bit of creative license, but it's always good to keep nicely in canon.