The height of the pedal pad from the firewall doesn't normally affect the brake pedal effort much at all. See the photo linked below.
The brake pedal needs to be at right angles to the pushrod when near maximum brake pedal force is applied. By "brake pedal" I mean a line drawn between the pedal pad and the pedal pivot point at the top. If the angle here gets to become much less than 90 degrees, this means that the pedal ratio is dropping and the car will be much harder to stop. In that case, move the pedal pad away from the firewall.
Moving the pedal pad to the lowest hole in the brake pedal will give the greatest pedal ratio and the least stopping effort.
You can use the pushrod length adjustment to affect the angle between the brake pedal and pushrod. Do this if the angle drops to less than 90 degrees under hard braking. If you lengthen the pushrod so much that the brake pedal hits something under the dash, stop. If you lengthen the pushrod any more at that point, the m/c piston will be pushed into the m/c bore which you do not want. The piston must be able to rest at its normal full back position in the m/c bore. You can improve the performance of the MBAK-10 a little bit by installing a return spring on the pedal. When you press on the brake pedal, your foot will have to overcome the force from stretching this spring, so it will add to the brake pedal effort. The job of the spring is to keep the weight of the brake pedal from pushing the piston in to the m/c bore. When you press down on the brakes and release them, the small spring inside the m/c has to pull all of the brake fluid back into it and push the brake pedal back. Adding in a second external spring will allow this to happen more quickly. The downside is a little more pedal effort when stopping.
If the pedal feels fairly firm and only moves 2", it is unlikely that there is any air in the system. Even if there is air in the system, it won't affect the amount of brake torque generated, unless it makes the pedal to pushrod geometry so bad (less than 90 degrees), that the pedal ratio decreases too much.
If you just assembled the car with new pads and rotors, it is not going to stop very well until the pads have been bed into the rotors. If there is any coating on the rotors, this will require even more time.
Look at the link below. Scroll down until you get to the section with the BP-20 pads. Look at the graph.
I'm not a fan of using different front/rear pad compounds. Look at the cf curve for the BP-20 in comparison to the BP-10. Once the BP-20 pad gets over 500F, its cf increases much faster than the BP-10 pad does. This is going to move the brake bias forward as they get hot. I can see doing this a little bit as you NEVER want the brake bias to shift rearwards as the brakes get hot. In my opinion this is too much correction. I would use the same pad front and rear in general. The bias should be set as much as possible by the ratio of caliper areas a rotor diameters.
I would probably use an E compound pad in the front.
Exactly what type of driving is this car going to be used for?