We were doing pretty much the same as you (car seat not bouncy chair) until DD was 6wo. However when we took her upstairs when we went to bed she wouldn't settle. It was at this time that I had an email from Johnsons about their baby bedtime challenge, so we tried it and it worked. Bath, change, milk, bed every night, first night it took 5 hours, second it took 4 hours and so on and by a week we could put her down and she would settle in about 10 minutes. There was a huge amount of rocking, cuddling, singing, stroking and patience to get to the sleep stage but it paid off in dividends. I also found two songs on youtube, rockabye baby sung by some kind of earthly woman with a great voice and relaxation music for babies which has a waterfall in the background and music playing over the top. These both really helped DD to settle and saved my voice - by the end of the week I'd lost my voice!!!
You say you don't want another sleep problem like feeding to sleep, I felt exactly the same as you until I spoke to my mum, she said "is it a problem, I thought all babies did that", reading through these forums I think a lot do. I taught myself not to think of things as problems but more the next step because as some point they stop it and something else comes along. I don't mean that in a patronising way, it's just what I've discovered along the way.
You could carry on as you are and there are many people who don't set a routine for their babies. I really feel that you have to do what works for you, whatever makes your life that bit easier. However I would imagine the longer you leave it (sleeping downstairs) the harder it will become to change the routine, because you do have a routine in place.
Can't help on the swaddling front we stopped at 1 month as HV told us to stop at 1mo as it stunts their growth, lots of info online supports this BUT plenty of people swaddle beyond this age and I've never seen them report anything to support this statement. Grobags are the bees knees!
Ceeveebee is right about sleeping in the same room, it helps regulate their breathing by listening to yours. I kept DD downstairs for naps during the day until she was 4mo (mainly because she wouldn't nap in her crib) and she moved into her own room at 5mo because she was so long she had outgrown her crib in our room. We did buy a sensorpad monitor though which meant it would tell us if she stopped breathing - I still don't know if they're good or bad because whilst they're very beneficial they turn you into a nervous wreck for the first few months if they go off!!