I would agree with both your statements. Really, if you were going to do the OMD retcon, I would think that there were better ways to take advantage of the new stories available to you.
I have to admit however, that I'm not a die hard fan when it comes to whether or not Pete and MJ have to be married or not. Maybe it's because I'm not from the Pete/ MJ marriage era. I can be fine with them either way. So maybe that influences my take on this a little.
My only major problem with getting rid of the Spider marriage is the way it was handled. A simple divorce would have worked just fine in my opinion. The idea that Spider-Man making a deal with a Satanic figure like Mephisto is a better, more relatable solution than a simple divorce is just ridiculous.
And no I'm not just saying this because I'm religious. I'm not religious at all.