Can't really tell how long it will last, I've seen them stay like that for a while but I've also seen them go quickly. The fact that it's growing is the major concern IMO. Given the present condition, my guess is that anything done to repair it would most likely hasten any potential failure.
Do you have (reefkeeping) friends or an LFS nearby that could "babysit" for a while? or at least be somewhat on call?
I can't answer question #1 but if you can swing it - I'd look into getting a 100-120gal basement tank to house the critters until you get a new tank, esp if you can't find a sitter.
HTH,
James