Boy, you have a lot going on! My three kids are all two years apart and that third baby is rough. I never had a colicky baby (although my middle baby did have reflux), so I can only imagine how exhuasted you must be! The sling recommendation is a good one. One friend had a sling that was really just a long piece of fabric and she could wear it different ways. I wish I'd had one with my youngest. He's now 19 months old and way too heavy to carry!
I'm going to disagree a little about scheduling. My opinion (and it's only my opinion) is that getting your baby on a flexible routine could help both the reflux and the colic by giving your baby's tummy predictable feeding and rest times. I will say that even if you start scheduling right from the beginning, it still takes a good 6-8 weeks to figure it out. It might take you a couple of weeks to a month to figure out what works best, given your baby's situation. But I found having routines to be a lifesaver for me (most of my friends scheduled as well to one extent or another). Obviously, you should be keeping track of your baby's "output" and growth, which you're probably doing anyway. And at this point, she's probably already moving towards some sort of routine on her own. There are lots of books on establishing routines. You'd have to read reviews to find the right one for you. The one I used (with all three kids) is pretty controversial, but it's not as bad as people think it is. And I modified it to fit my baby and my lifestyle, as you should with any book on any parenting issue.
Considering your whole situation, I think it would be worth giving scheduling a try. Some babies really resist it and it's not worth it to add to your stress by feeling like you're fighting with your baby! But, it could be a huge relief for you if it helps. :) A crying baby is really stressful for a mom, so I hope you're taking care of yourself (by getting a long massage or whatever relaxes you - LOL) in addition to caring for your kids.
Good luck!