I don't think using a tube designed for up to 28 mm tires in a 32 mm tire will have dire consequences. I've done something similar. Change it when you get an opportunity.

Goop worked? I'd be afraid that if the stem moved at all (like during inflation) the goop would loose its grip and you'd have a leak. Don't know though. I'm not sure I'd want to depend on that to get me home. I'd probably be wishing I had just bought another tube.