I did the test shown at the link for the booster where you pump the brakes several times, push down on the brake pedal and hold, and then start the car.

I pushed the pedal 5-6 times and then pushed and held. The pedal slowly dropped almost 2 inches. This seems to be the master cylinder, and not air in the system. If it was air it would not have taken the 5-6 seconds to drop the 2". It may have dropped a little more when I started the car, but not a lot.

I don't think the booster is ruptured, as the brakes are not too bad with any amount of speed.

I am going to bleed the brakes anyway, and check the calipers again, but
I looked at my calendar, and it may be a month or so before I check in again.