It's fixed! Let's celebrate!
I can hardly believe my previously inexperienced-at-plumbing dh actually fixed our leaking pipe problem. He was very clever. Rather than ripping up the floors to find the leak, he simply rerouted the pipes and shut off the leaking one. It took him about a day to do it. Next is insulating all the pipes, but we're not stressing about that yet, as the chance of freezing temperatures here seems to be gone.
If you're curious about what he used, here's the video on youtube that showed him the right pipes & fixtures to use. Apparently they were extremely user friendly and required no soldering at all.
He even reduced the water pressure, which makes it much easier to avoid going at full blast whenever I turn on the faucet. Thanks honey!