You were right with the clues you had. At this point you'd have to do a process of elimination. There are only two possible answers for 1950 (8.5 and 8.9). If you choose 8.5 you won't be able to solve clue number 6, which says that 49 seconds comes 6 years before 84 seconds.
I'm not 100% sure on the answer but this one looks close: