If the control surfaces were not working on the left wing at that time, it would have had a hell of a time keeping trimmed out and would be fighting to make the turns that it was being asked to do. The computers would likely begin to over correct and gradually loose control. (which it did)
I don't know of 80 degree turns make sense. Where did you read that? Here is what I dound on the standard de-orbit procedures:
The commander begins the de-orbit burn by firing the orbiter's engines to slow its speed and take it out of orbit. Using the RCS engines, the orbiter is turned around so that it is moving backwards at a slower speed. To maneuver the orbiter while it is in this position, the commander uses the RCS engines to control roll, pitch and yaw motions. The OMS engines (space engines) are then fired, taking the orbiter out of orbit and thrusting it into the earth's upper atmosphere. The RCS engines are used one last time to turn the orbiter around so that it is moving nose forward and pitched up slightly. In the upper reaches of the atmosphere the vehicle's motions of yaw, pitch and roll are controlled by the RCS engines. As the atmosphere thickens, the airplane control surfaces become usable. The orbiter re-enters the atmosphere at a high angle of attack (about 30 degrees). This high angle of attack is used to direct most of the aerodynamic heating to the underside of the vehicle where the heat resistant tiles give the greatest amount of protection.
At an altitude of approximately 30 miles, the orbiter makes a series of maneuvers and S-turns to slow its speed. At 9.5 miles in altitude and at a speed of Mach 1, the orbiter can be steered using its rudder. The on-board computers fly the orbiter until it goes subsonic (slower than the speed of sound: Mach 1). This happens about 4 minutes before landing. At this time the commander takes manual control of the orbiter and flies a wide arc approach. At 7.5 miles from the runway, the orbiter is flying about 424 miles per hour at an altitude of 13,365 feet. About 2 miles from the runway, the orbiter is flying at nearly 360 miles per hour on a glide slope of 22 degrees.
Once lined up with the runway on approach, the orbiter continues its steep glide slope of 18 - 20 degrees. The commander levels the descent angle at a final glide slope of 1.5 degrees by performing a ``flare maneuver''. The nose of the orbiter increases its pitch (noses up) which slows its speed. The orbiter touches down at a speed of about 215 miles per hour. It is slowed and eventually brought to a stop by the speed brake, wheel brakes and a drag chute.
It is this unique aerospace vehicle, a lifting body, that launches like a rocket, orbits like a spacecraft and lands like a glider that continues to link earth and space.