Yes playing standing up is definately tougher then sitting down. When I started really practicing, I decided that I didn't want "two playing personalities", that is, a good player who sits and a not so good one who stands, so I always practiced standing. Now, standing is actually easier just because I'm used to it.

You'll get used to it too, it's not too hard. You just have to get used to the new hand position.

As for floating or anchored pinky; well this is a question that many debate. Guitar masters have used both techniques, so the best advice is to do whatever feels right- neither is more correct then the other. Personally, I've never anchored my pinky.