I'm not modding, I'm improving
First point, don't drive at 75mph?
On a more serious note, sounds like tracking to me rather than wheel balance. You are more likely to get vibrations all the time if the wheels are not balanced correctly.
When was the last time you had the car setup/tracked?
Also, re the braking question, checked your pads/discs? That is the most likely cause I would have thought.
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