<I never really understood why Dougal wanted to kill Jamie in the books, but if he’s got an unrequited thing for Claire, it makes more sense.>
I got that in the book. Dougal wanted to kill Jamie because Collum’s life expectancy is compromised by his illness. If Hamish has not reached majority then both Dougal and Jamie (as Ellen’s son) have right to the Chieftanship (is that even a word?) The Clan could vote Jamie as Collum’s succesor. Very clever of Dougal to arrange the marraige between Jamie and Claire, as Collum points out, the Clan would not have Jamie as chief with an English wife. Thus Dougal has eliminated the threat without killing him.