He didn't invent it. Valerie mentions using the stuff long before he was around (iirc, back in HER college days).
Yes, because the rest is bonus material, like booty calls, extra pictures, etc. Kinda like how if you completed the story of ToN but didn't do extra stuff, the game was only about 80% complete (Second playthrough, I didn't do the bonus stuff and was confused the game was almost over when I was at 77% completion)
Yeah, I was rather annoyed this game never introduced teleporters. While there are more ways to get anywhere, the map is convoluted enough for me to get turned around, particularly in either the mansion or the underground portions.