How much matter was ejected when the Solar System formed?
It is actually the other way around:
First a massive accretion disc can form, through which material looses angular momentum and accretes onto the star radially, hence being angular momentum poor.
However, during the initial free-fall phase, before the disc forms, infalling material can be 'rejected' at the star, either via high pressure gradients or magnetic interactions. This causes a polar jet to form around the protostar, which emits material back into the interstellar medium. Measured jet mass-loss rates are up to 1/2 the measured accretion rates.
Furthermore, the remaining fraction of material that did not form planets is ejected at the end of the disc lifetime via photoevaporation by the young stars' X and UV photons. What fraction this is in comparison to the mass in the planets is unknown, as the overall planet forming efficiency is unknown.