I don't know about the effects of mixing the booster and the MC. Putting that many different model parts together just doesn't seem like a good idea to me without doing some heavy research on what can adequately supply to downstream components and how you maintain that system.

However, the ABS and the squealing sound like a different problem. That's new since you just installed the textar pads recently, correct?

It sounds like you've got something put back together wrong or the complications of different components are coming home to roost. Are you sure that the caliper size and rotor size and the pads are compatible? Did you disconnect an ABS sensor and not get it back in right?