Extremely low brake pedal

Was this the problem when you started?

Please go back and check your calipers for me. I need to know if the brake bleeder is on the top of the caliper or the bottom.

Here is a guide that can help

https://www.2carpros.com/articles/how-to-bleed-or-flush-a-car-brake-system

and

https://www.2carpros.com/articles/brake-pedal-goes-to-the-floor

IMPORTANT:

* Use the two-person bleed procedure under the following conditions:
* Installing a new Electro-Hydraulic Control Unit (EHCU) or new Brake Pressure Modulator Valve (BPMV).
* Air is trapped in the valve body
* Do not drive the vehicle until the brake pedal feels firm.
* Do not reuse brake fluid that is used during bleeding.
* Use the vacuum, the pressure and the gravity bleeding procedures only for base brake bleeding.

TWO PERSON PROCEDURE

1. Raise the vehicle in order to access the system bleed screws.
2. Bleed the system at the right rear wheel first.
3. Install a clear hose on the bleed screw.
4. Immerse the opposite end of the hose into a container partially filled with clean DOT 3 brake fluid.
5. Open the bleed screw 1/2 to one full turn.
6. Slowly depress the brake pedal. While the pedal is depressed to its full extent, tighten the bleed screw.
7. Release the brake pedal and wait 10 - 15 seconds for the master cylinder pistons to return to the home position.
8. Repeat the previous steps for the remaining wheels. The brake fluid which is present at each bleed screw should be clean and free of air.
9. This procedure may use more than a pint of fluid per wheel. Check the master cylinder fluid level every four to six strokes of the brake pedal in order to avoid running the system dry.
10. Press the brake pedal firmly and run the Scan Tool Automated Bleed procedure (below 15,000 GVW) once, or run the Function Test (above 15,000 GVW) four times. Release the brake pedal between each test.
11. Bleed all four wheels again using Steps 3 - 9. This will remove the remaining air from the brake system.
12. Evaluate the feel of the brake pedal before attempting to drive the vehicle.
13. Bleed the system as many times as necessary in order to obtain the appropriate feel of the pedal.

I had this very same problem with our 1999 Tahoe and it took four two person bleed cycles to get all the air out of the system. I decided my Tahoe was a freak with a hidden lung by the time we were done. Keep on bleeding and have a third person monitor the master cylinder so it doesn't run dry FOR SURE. I know it's frustrating cuz I have been there.