In that case, weather is going to be your problem from the get-go. Book from EWR (CO has better inflight service) and plan on taking the train from BOS to EWR Amtrak Station as a backup in case of WX in Boston.

Adding flights from BOS to IAH is risky as that flight could have a problem, or your routing might need to connect in EWR first anyway - adding even more risk.

Be proactive - I had a flight scheduled from IAH to EWR one year when IAH was threatened by a hurricane. As soon as it became even remotely possible the flight might have a problem, I switched to EWR before that flight become sold out.