Hello again. Around 60 mph I hear a higher-pitched whirring / singing noise.

You may have a bad alternator. Remove the belt and check for play.
The tires may be making noise from the suspension being out of alignment. From what you describe on the tire wear and noise, it sounds like the toe or total toe adjustement may be off and tht can make the tires wear like yours have. They might have to be replaced if they are realy worn badly as they will continue to make noise in sme cases.