Brake Disc Caliper problems of the 2005 Buick Rendezvous

Intermittent loss of power, loss of abs brakes and loss of awd. When you apply pressure to the gas pedal (accelerator) if you depress the pedal for what feels like over a 1/2 inch you lose power and the rpms go sky high and you can hear it trying to rev up. To get going you have to release the gas and press lightly. I loss power, esp. Going uphill since it needs more to go, but you can't give it more gas else it won't go. I and my fiancã© were almost hit in an intersection because of this loss of power. You can gain speed, but very slowly and anytime you depress the gas pedal further it again fails. Replaced three wheel bearings, all brakes, two calipers and the throttle position sensor. Nothing shows on the readout except for the front bearings aren't reading right, but they're brand new and have been re-checked for defect. Still that hasn't fixed the issue. Upon problem has actually been occurring for almost two months now.