Jo -
Have you tried stopping mid-feed to wind him? He might not really be happy about it, but it's a tip our hv gave us for Romilly. She was really hard to wind, and like Sam, was ending up bringing milk back up. We started winding her mid-feed yesterday, and it has really helped in terms of settling her. It's worth noting that the Infacol can take about 48 hours before it'll start working, so try and stick with it
If it's really not for him, there are other things you can get, like Colocynth granules and so on - your HV (if you ever get to see her!) should be able to recommend some.
Also, try pedalling his legs. Not like he was on a bike, both legs at the same time, but just gently sort of pumpthem up to his tummy and out again. If he resists you, just leave it, and try again another time. You can also try very gently massaging his tummy - in a sort of arc above his belly button (as if you were drawing the sun's path across the sky from sunrise to sunset). Not too hard, obviously
How often is Sam feeding? I'm only asking because Romilly rarely takes more than 2oz per feed, but she tends to only be 3 hours at most between bottles.
It's normal for babies to lose weight after they're born, so try not to worry about that 4oz - that's pretty much what Romilly lost too. She's since put it back on. I hope that Sam has done too when you get him weighed tomorrow.
Sorry for the long rambling post, just hope you find something to help with his wind soon