Turns out we're not so screwed... at least for now. Our builder is paying for everything except the work that the water damage folks did to dry out the crawlspace and treat for mold. They aren't paying that because they "would have done it themselves if we had just waited." So I'm out $150, but it could be a LOT worse.
The builder informed us that our washer was not, in fact, leaking. Rather... the plumbers simply neglected to finish their work back in 2002 when the house was built, and therefore, our washing machine has been draining directly into our crawlspace for 5.5 years now. Lawsy.
So they've installed the necessary pipes and they have promised to fix the support beam, then the garage floor. So we don't have to file with insurance or anything. Huzzah.