I was actually a little surprised that Richard only goes back to the late 1800's. I just assumed that he had been around for thousand's of years.
At this point, I don't know weather or not to believe Jacob or the guy wearing black. I guess the writers are trying to portray what the characters are going through in not knowing who to trust. I could see this ending with Jacob being the deceitful "bad guy."
If Hurley can see and talk to Jacob than couldn't Richard's wife be Jacob in disguise saying that the guy in black must be killed?
At the same time, Locke killed all those people at the temple which makes it hard to believe the guy in black is good either.
I guess I'll just have to keep watching and see how it plays out.