It sounds as though your car may have the wrong spheres fitted, as when
the spheres loose pressure this will make the ride a lot harder, but
this will not cause the pitching up and down.
How does it perform when pulling away fast ? Do the rear mudflaps hit
the deck ? If so this could lead to the same assumption.
As for the vibration under the brake pedal, does it fell like you have
trodden on a bee ? ie buzzing slightly from under your foot, if so you
probabaly have cheap LHM. Get it out and refill the system with either
Castrol or Total LHM. In my past experience all other LHM is pants and
too thin, it works ok but the buzzing is the spool in the brake valve,
this is damped out if you use decent LHM.