The other surviving ships were probably doing their job, keeping the bulk of the TIE fighters busy. Nobody on the Death Star, (except maybe Tarkin's aide!) had a clue the Rebels were trying to hit the exhaust port.
Even if Wedge could somehow slam the brakes in front of the pursuing TIE's, they would probably blast him before he could hit and a pilot of Vader's skill would avoid a collision anyway. Wedge saved Luke's bacon once in the battle already. If he was faking a malfunction, he was taking a big chance he wasn't going to have to return to base and have a mechanic look over his X-Wing. (Or "ask" his Artoo unit what the problem was!)
Wedge was certainly no wuss on Hoth or in the second Death Star attack.