hun - he is still soooo little - dont worry about creating any "bad habits" until closer to 12mths.

do whatever works - if he needs to sleep in the sling - let him! He's getting sleep! lol
Try not to worry about what anyone else says. I know its hard.

DD#1 was fed to sleep until she weaned at 14mths - now she is a 3 yr old who goes to bed happily at night
DD#2 is in the transition from being rocked to sleep to going to sleep in her bed. But she sleeps well in her own bed after co-sleeping part time since she was little.

Sorry this is a bit jumbled - I'm juggling the girls atm