Don’t worry about messing up the boots. If the bolts are that bad, cleaning them up won’t matter much, within a year or so you’ll be back in the same boat. It’s going to need a new caliper.
You need an impact or a long breaker bar. If you wreck the bolt heads, you’ll need to torch it apart.
This guy says you need a long bar and another guy says try whiskey and I say, good advice.
Go to a long bar, drink whiskey, let the auto shop put on the new brakes, get a cab to take you home, take 4 aspirin and call me in the morning.