Ok, I have some suggestions. After he wakes from his catnap at 6:40 or so, I would keep things VERY low key. I would snuggle him when he wakes up, then get him ready for his bath. Give him his bath, a little massage in a darkened and warm room, then into jammies. Then I would feed him the last feed before bed RIGHT before you put him down so when he goes into his crib he is good and ready. If he wakes 45 minutes later, go in, pat him or do whatever he responds well to. You may have to pick him up and get him completely drowsy again then put him back in the crib almost asleep, if not completely asleep at this age. Keep doing that until he stays there. I would stick to this schedule every night for a week at least. Do not stray fro mit. His internal clock should be adjusting by that time.
His awake time at 9 weeks should be no more than an hour. I think he is getting overtired and thus his body is having a hard time shutting down and staying down. The more over tired they are, the less sleep they get. I would watch his sleepy signs very closely and try to get him in bed no more than an hour after he wkes. Forty-five minute naps are killers, so be consistent with trying to extend them. I think if you catch him in the right window it will help. You might try going in a little before he wakes to settle him back to sleep at that 45 minute mark. I don't know what you're trying but that seemed to help my lo.
Hope these suggestions help! Keep me posted