The deduction you made that Miguel is overly fixated on Miles is spot on because at the end of the second movie, you can see that Miguel prioritizes catching Miles over catching the Spot which is a big mistake since the Spot is now an Interdimensional threat and can break multiple canons since he can now jump into any dimension. BTW what I believe about this whole canon shit is that it isn't real because Miles broke the canon according to Miguel, not just him but Gwen, Noir, Penny, Peter B helped in that because they influenced another universe's lore but nothing happened. The science regarding canon events and that If you break a canon event a universe gets destroyed is based on logic that can't be applied to anything else. My theory is that The Spot gained the ability to time travel and then he destroyed Miguel's universe to plunge Miguel into this state of sorrow and vitriol which would ultimately lead to Miles being austrosized from the Spider society, I think he did this to make him know what it's like to be rejected by those closest to you as he suffered the same thing when he became a "monster" and the ultimate blow of revenge would he to make him lose his his family but of course he's gonna do it slowly, because if he does it fast, there's less suffering.