Matzah Obligation?

I didn’t grow up with Passover, and have been working my way up to proper observance over the past couple years. I have two related questions about matzah: 1. How much matzah are we obligated to eat? The answers I’ve found online seem to vary from “an olive-sized chunk, during the seder” to “more than that, during the seder”. But I have heard many people online and at shul talking about matzah like they are (or feel?) obligated to eat a pound a day during Passover. A million recipes for using matzah, buying huge boxes of it, working it into every meal, complaining about the havoc it wreaks on their digestive systems. Does this stem from any halachic requirement, or is eating matzah beyond the seder just tradition/the spirit of the holiday? 2. My partner bought a box of egg matzah this year, and I noticed the box says something about not being suitable for Ashkenazi Jews unless medically needed. Does that mean egg matzah is “Passover-treif” like chametz, or just that it can’t fulfill the halachic requirement to eat some particular quantity of matzah?