The biggest thing that goes against this how long do you have to spend in a universe that isn’t your own for it to collapse? How many portals need to be opened to and from there before you rip a hole in the universe? I was all in until you reminded the spider society is literally operating in one universe! They have not destroyed it!

Edit: It’s far more likely that only the people of that universe are allowed to change there fate so Miles interfering himself was the problem in that universe not saving the Captain! That’s why when Gwen’s dad quit being captain it didn’t destroy the universe. You’re theory makes a lot of sense! But Dr.Strange in “What if…?” On Disney plus changed an absolute point and destroyed his universe pretty similar to what we see in the movie. So these things that are meant to happen in everyone’s story. Honestly who knows at this point.