New teats can take a couple of feeds for them to adjust to the new flow, keep him a bit more upright in your arms until he gets used to it. If he has a lot of gas there are drops you can get that help the gas collect into bigger bubbles which make it easier to get rid of.
It's still really early days yet, he's still adjusting to being in the world and his digestive system is adjusting to food! I agree with keeping feeds to 3 hourly as much as possible during the day. Have you tried a paci, he may need to suck which could help the night.