As far as we know, the battle posed no risk whatsoever to the E-D.
Actually, that's the point of the entire sequence, of Bok's plans, of the personal threat to Picard in general. Bok wasn't planning on killing Picard, he was planning to get Picard to kill his own crew and thus share Bok's pain of loss. Killing Picard would have been as easy as planting a bomb in his quarters when he took over Stargazer; getting him to destroy Enterprise was the point.
The only way Bok could make him do it was to make him relive the Battle of Maxia and use the Picard maneuver, to which there is no defense. He also made sure that the ship was "otherwise fully armed" except for the torpedoes it fired in the original battle.
No one on the bridge even hints at the suggestion that Stargazer wouldn't be a threat to Enterprise. On the contrary: if Data hadn't been there to devise a counter-move, Stargazer probably would have crippled the Enterprise and Bok would have rewound the tape and gotten Picard to perform the maneuver a second time, just to finish them off.
Depends what you mean by "a viable counter". Riker was looking for a tactic to stop the Stargazer in its tracks. If you turned and ran at high warp, then a high warp hop and stop from your opponent in your direction wouldn't put them on your bow, especially since the E-D was undoubtedly the faster ship of the two! (Moreover, it wouldn't have fit with Picard's relived memory. He'd have placed himself on the "bow" of/fired at a patch of empty space)