E.E.
I'm another one who would suggest a carrier. Personally I (and my son) liked a ring sling. He didn't sleep anywhere but my lap (or in the car) for the first year of his life. Granted I didn't have another child to take care of, though.
Do you have a swing or something? And you mention that he sleeps in the bouncy - is that where you're trying to put him for his nap, too?
Have you tried to book The Happiest Baby on the Block? Maybe you can use some of those techniques.
Good luck!