I am not going to get dragged into it but most of these are easy to understand. And yes, it seems like you are reaching to try and understand the film.
Like this for example.
Originally Posted by itsaboutthattime
Mystique: "trask is the enemy"
Magneto: "killing one man isn't enough"
But dude literally just a couple mins ago thought killing 1 mutant was enough
Magneto was fine with killing more humans because the hatred extends more than Trask, there are plenty more humans that hated mutants and it doesn't end with Trask. Also in the original timeline, Mystique kills him and captured her and then Trasks' company creates the Sentinel from her DNA. Another example is that Stryker also continues Trasks' work of being against mutants. So yes, he wants more humans dead and believes one is not enough just by the simple example of Trask dying and the Sentinel program still going through.
Magneto was also fine with killing one mutant, Mystique, because she was the catalyst for the Super Sentinel Program. From his knowledge, no Mystique means no unstoppable Super Sentinel in the future and that is one gigantic threat to the mutants prevented. Pretty much kill one for the save the mutant race.
Plus Magneto never really said he would only kill Mystique, he tries to prevent to kill his own kind but if there are more mutants that becomes a threat to the rest of the mutants, I am sure dude would kill that mutant too without hesitation.
I mean the movie doesn't need to spell all of these out, you got to be able to connect some of the dots together.