Nope, when you switch it clears any positive rep in that one down to zero, so you'd be back at zero again.
The real question is would you get points for those first ranks again for your old faction, or would you have to rank back up to get points again...
yes you would get points but the points scale along with the rank so there is no difference in going from say 9-10 and getting 10 points than there would of been going from 1->2->3->4 also 10 points
i think its 1 point per 5000 regardless of rank