CO really needs to step up. I can see if this was an award ticket but really? Paid BusinessFirst and they're not budging? If I were running things anyone on a paid BF ticket that included a USH segment would be booked in a limo from any Manhattan location to EWR. All you're asking for is a reaccommodation to a later flight with open seats. How would that hurt CO's bottom line? This should be treated as a schedule change. The departure time from EWR no longer meets your needs. It shouldn't matter that it's not CO's schedule change. If any other codeshare partner, including ExpressJet and Colgan, were to cancel a flight they'd put you on the later flight from EWR no questions asked.

Keep calling until you get what you want. At some point they'll realize that the cost of answering your calls exceeds what they might lose in revenue by having an unsold seat on the earlier flight!