Sorry to just now be getting back to you...it was a busy weekend!
I think that the important thing to keep in mind re: sleeping in the sling, is that eventually, yes, there will be some transition. It all depends on how long you wait to tackle it. If he's under 6 months, the transition should only take a couple of days...after that, it does get a bit more difficult.
Your LO isn't sleeping in the sling at night, though, so that helps. When DS was little, he took every nap on a person or in his bouncy chair; I finally stopped that when he was about 2 months old, and I don't remember there being a problem because we used shh/pat.
Re: adjusting EASY...well, I always tried to do the best I could. If it was his E time, I fed him, regardless of where I was (he was bottlefed on those occasions). If it was his S time, I hoped that he would fall asleep while we were out, which didn't always happen. The best thing you can do if you miss his sleep window and he's OT, is to APOP that nap, and reduce the next A time (basically a feed, diaper change, right back down). That was the most helpful thing I ever learned with EASY. The times might not be "perfect," but all that matters is meeting your LO's needs and keeping the general pattern.
HTH! How have the past couple of days been?