No one got back to me
w/ similar experiences, but yesterday we took apart the couches (30 mins), took the upholstery back after 8 months, and the Ikea Returns person very politely took the material back (we showed them the broken zippers and the melted fabric), and replaced them with brand new grey washable fabric, which is a little like denim. Not only that, but the cost ended up less, and we got a $100 gift card. So I guess complaining was OK.

It took another 90 mins to cover and reassemble everything (longer with kids, trust me), but now it looks great.
For anyone who might buy this, the salesperson recommended after washing to actually put the upholstery on while it was still damp, because it was too hard to do when completely dry. And since we have two kids, we'll probably be doing this a lot.
Hope this helps someone in the future!