Bubble, I've only quickly read through all this but here's my 2-penny's worth.
The first stop is to ensure that he doesn't have reflux - see your GP. Propping his cot mattress up with a towel at one end may be enough. Even for babies with reflux, The Canadian Paediatricians don't recommend your baby spends more than 2 hours a day in a car seat - there wee heads are waaaay to heavy!
The wind theory - it's pretty much been rubbished over here in Canada. None of the health professionals believe babies scream due to wind. There are numerous studies that show "colicky" babies contain no more gas than settled babies. The crying however causes them to temporarily injest more air. There is also concern as to what harm these colic draughts are doing to babies tummies.
However, SOME babies develop a distinct dislike of the gastro-colic reflexonce they start taking in more milk. When a baby feeds, it stimulates movement of the bowel which can cause discomfort. Parents think their munchkin is 'gassy' because they can here the bowel moving. You can help this by feeding smaller amounts more frequently and lying your baby on its left-hand side, so there is no twisting of the digestive tract (entails a football hold on one side).
At 3 weeks, cluster feeding begins, along with a start of evening fussiness. My DS had all the fussiness your baby is showing. It only lasted a couple of weeks. What helped was a calming evening routine - all lights dimmed by 5pm, bath, cosy feeding for a couple of hours then bed.
What has been shown to work for fussy babies, time and time again is swaddling with the 5 S's (see Hunker's 11:33pm post). Some babies need swaddling for 3 months! My DS was swaddled night and day (especially during feeding) for 8 weeks then was able to do without, as long as I didn't let him get over tired. There is a method of swaddling with 2 blankets to ensure no arm escape (triangles go over the arm then under the back, forming little arm loops IYSWIM). I bought a miracle blanket - boy did it work!! Warning though - if your baby does have reflux, then jiggling is obviously a no-no. Those electronic swing seat things are better.
Some mums over here swear by attachment parenting - baby in a sling all day and co-sleeping etc. I wasn't too keen though as DS is a right old noisy sleeper! I do tend to have him in the Bjorn for most of the day though.
I would be more than happy to send you my miracle blanket but it's probably going to take about 10 days to get there? I have a spare Bjorn as well. CAT me by all means.