Orange Girl World

Can any explain the series finale of “Doctor Who” for me?

I watch “Doctor Who” because David Tennant is hot.  I think I have basic grasp of the show’s history and mythology.  However, I am not a huge sci-fi fan, and the last show in the series left me puzzled.

Why would the Daleks want to destroy reality?  I thought they liked to conquer planets and make people slaves and stuff, wouldn’t destroying reality defeat their main objective?

Also how does touching the Doctor’s hand in a jar cause another Doctor to grow?  I get that he transferred all his regenerative energy into it, but how does touching it cause anything to happen?  And if it really is that easy to grow a new Time Lord , why don’t they do it all the time?

Your answers please…