If two players have the lowest threat which one of them will carry out the old world card?

Also,when Khorne kills a figure with the card Blood Frenzy which enables him to roll two dice before combat in a region does those figures advance his dial?

Thanks!

Regarding question 2, it won't advance the dial, but it will give Khorne a dial advancement token (i.e., Khorne will get one dial tick for sure, and a second one if he has more dial tokens than any other God).

Regarding question 1, I don't think this can happen. The threat levels are all unique. If you check the dials you'll see that each one doesn't go up 1,2,3,4 etc. Each one 'jumps' from one number to another, several points higher. This means that no two Gods will ever have exactly the same threat level. (I think this is correct - I haven't got my board open in front of me.)