To my understanding, there are many kinds of ticks that will bite anything warm-blooded (including people and dogs), so to be safe rather than sorry, I would assume all ticks carrying Lyme can infect humans.
I haven't read anything to the contrary. I don't know if there are any meds to give animals to prevent Lyme, but I don't think there is -- and the vaccine developed for humans some years ago didn't really work.
I heard the same thing. You can get Lyme from the fleas on your dog.