Steering wheel shake on highway speeds

The most common suspect is a broken belt in a tire, but that is usually also felt at real low speeds. The next thing is to measure "lateral run out" for each wheel with a dial indicator. If run out is excessive, first look for a bent wheel. If it is okay, look for debris stuck between the wheel and brake rotor, and between the brake rotor and hub. A brake rotor can also be warped in such a way that it will cause the spindle and wheel to shake. That will likely not be felt in the brake pedal.

Tire cupping is due to an alignment problem and will affect both tires approximately equally. Part of the problem is the engineers at Ford have left off one of the main adjustments to save money. If "camber" is off, you are stuck with what you have. The only remedy is to replace bent parts, but other than the tire wear, misadjusted camber will not cause a vibration.

The next direction I would be going is to suspect a worn strut that is failing to dampen the normal tire bouncing. That will show up at the speeds you observed but not at lower speeds. Worn inner CV joint housings will cause a steering wheel oscillation, but that mainly occurs when accelerating, and more so at lower speeds up to about thirty five mph.