The thing in the middle is a dust cap. I usually use a flat head and a hammer to pry it off. As for the caliper bolts, get the car as high as you can, spray it up with some PB Blaster and use a breaker bar to get the leverage you need. Also, unlock the steering wheel, and turn the wheel one way or the other so you can reach the bolts easier. Hitting up the bolts with a torch works well too. Just don’t melt the rubber boots on the caliper. To get the rotor off, you’ll also need to remove the caliper bracket. That too will have bolts that’ll be pretty tight. Inside the dust cap there is probably a nut and cotter key. Those should be easy to take off, as there is usually a lot of grease inside the cap.
Good luck!
Elevation of the car and leverage are your keys!!