Do you know if the former owner did any work on the swinging arm? I note that you had some side play on the swinging arm and had to tighten up the rear wheel bearing preload to fix this, which is slightly unusual. One thing which may be causing bad handling and cornering is an incorrectly assembled swinging arm assembly, which can result if a previous owner has followed the illustrations in the Spare Parts list.
When I got my '69 Daytona it had weird cornering problems, caused at least in part by old hard tyres, but mainly by incorrect assembly of the swinging arm such that the thrust washer was on the outside instead of the inside of the right fork next to the shims. This incorrect assembly allows the swinging arm to move up to 0.1" sideways. The workshop Manual
drawing is correct but the Spare Parts books of all years from '69 onwards are plain wrong.