Oh, been there twice - hope I can help, even if just a little.
Sounds to me like a pain issue - you've tried "happiest baby" and it didn't work and even Dr. Karp himself said it wouldn't mask pain or other real issues. Look at possible pain probs:
1) As for formula, I don't really know much there 'cause I nursed my two mostly, but I used Nestle Good Start when I couldn't 'cause it has the "comfort protiens". I'd discuss this issue more with the dr. Sounds to me that this might be an issue. If you switch to soy, make sure to ask him about what nutrients it may be lacking that you may need suplemented in (even if at a later date once the baby calms a bit).
2)It still could be acid too though! My kids had an acid issue also and the meds worked a bit, but didn't totally take care of it, so we had to switch to a stronger med. They didn't really spit much, but coughed/choked on the acid and would scream. They both only liked to sleep in an "up" position, with my daughter and first born being the worst. She never slept more than an hour and almost always slept in a sitting (almost-90 degrees) position. I put her in one of those activity centers out of desperation when she was screaming one time and she feel asleep in it 'cause the chair was a real 90 degree chair.
3)As for the chiropractor, I am a firm believer that if you are out of mis-alignment, you may become sick 'cause it restricts your bodily functions. I LOVE chiropractic care for myself (esp. during pregnancy-it helps with easier deliveries) and though I never used it on my kids after birth (cause I never thought about it till they were out of that colic stage), it was brought to my attention after they out-grew colic and I nearly hit myself for not trying it. I have no doubt that it would work. You said you had a long labor and ended in a C-section. I don't think the C-section procedure has anything to do with it but the fact that baby was in the birth canal for a long period of time I think does. When you look at models of a baby birthing, you can tell that they are contorted. The longer they stay in that position, the more likely they are going to need to be re-adjusted (same being the more likely their head is conformed/cone-head). You must remembe that babies are extremely loose jointed. THis allows their bodies to easily manuever through the birth canal, so that is good. BUt it also makes them highly vulnerable to dis-alignment from birth or to become dis-aligned for a good long while after birth (approx. a year from what I've heard), so re-alignment is not only necessary to keep them straight but is done easily (since they are still loose jointed) and should be done often if you believe a mis-alignment is the prob. Chiropractic medicine also works wonders on ear infections and many other ailments. Ask any good chiropractor what it treats or do some reasearch on-line. My biggest suggestion is find a chiropractor that is well-used to working with kids with ailments. I think you will find results!
Hope I helped!
T.