I have tried begging, pleading, bribing, yelling, screaming, throwing tantrums.. all to no avail. Am I the asshole for trying to pressure my wife into something she's clearly not ready for? Judging by her actions she is absolutely sandbagging us, yet she keeps saying to my face that she wants to buy a house. I have wasted a full year of my life trying to hunt down some magical fairy hobbit hole that she would say "yes" to but at this point I want to cut and run.

Sounds like you already made a decision and are looking for validation. But if you want to work this out, you need to drag your wife into couples counseling to work through the issues (including MIL... People don't just decide ti hoard for no reason, there's some past trauma that may be affecting your wife a different way) NON-NEGOTIABLE. For your daughters sake, for your sake, and for your wifes sake.

Do you want your daughter to grow up like this? In filth with a mother you resent? She's 4. If she hasn't already, she's going to know Mommy and Daddy don't get along. Then she'll end up thinking it's her fault and end up having a self sabotaging way to deal with it.