Well, Jakob Ammann, who the Amish are named after, was a member of a Swiss Brethren church (now called Mennonite) who didn't think his Mennonite brethren did enough shunning (a core principle of the Swiss Brethren).

So he formed his own church. Eventually members in his church (surprise!), shunned him over some different differences, as it happens when you join a group with all the cantankerous people. And it continued so on and so forth.

The distinctions might be in practical matters that arise over time--like fabrics used in their dress, use of buttons vs hook fasteners, or use of technology, or use of English vs German, but theologically they're pretty much identical and these differences are just natural things that happen over time.

An Amish church split is really just two groups mass shunning each other. There's no real difference.

And I'm aware it probably doesn't seem like that closer up, because I'm speaking very abstractly. But I can't see how anything you've said disagrees with what I've said.

And, I want to say I do appreciate hearing your experiences. For the record: I have a degree in Bible, did some post-grad study on church history, have some family members who are Mennonite, and grew up pretty close to a large Amish community.