To answer your question about the Durability of an EVA unit, each is protected by what's known as an "AT Field." Even a weak AT Field, generated by a weaker Angel can survive multiple near-simultaneous Nuclear detonations at point-blank range. The AT Field of EVA-01 is multiple orders of magnitude stronger than that, and can, in theory, only be breached by either another AT Field, or by specific, uncommon weapons. Plus, the EVA, as a pseudo-living being is also capable of self-repair.