I've seen claims about buckets of water, vinegar, and cut onions helping with freshly painted rooms. But that's all. Is there anything I can do to make these fumes go away? Or am I doomed to stay with my in-laws for the indefinite future?
As Tester101 said, first step is isolating your house from them: close doors, windows, garage, and so on.
Next step is dealing with those vapors that do come in. Have you tried activated carbon filters? They make ones that fit in your air handler. These things can absorb amazing amounts of organic vapors.
As for the sealer, it will off-gas the volatile components at a first order rate (I think, someone may correct me), which means it has a half life. The amount will drop exponentially over time. It should get better,but there's not much you can do to speed it up.