And to address the "is VMCA fixed" question.
It is permissible to schedule VMCA (and VMCG) with altitude and temperature, to reflect the reduction in engine thrust that results, so as to avoid excessive penalties to hot/high operations.
But it IS true that VMCA is "set" in the sense that once determined for a give alt/temp, it is then applied for all instances of that temp/alt. That is, heavy aircraft must use the VMC(A/G) applicable to a light aircraft; you can't schedule with aircraft weight.