My son's 26' schooner had the same problem with internal scrap steel/concrete ballast, except that it was even worse. The fiberglass
covering it on the inside was very poorly done, so the ballast got wet often. We injected epoxy
into all known voids, added several layers of glass to the outside of the hull
from bow to stern to halfway up to the waterline since the original glass was quite thin and had deteriorated, glassed over the inside from bow to stern of the ballast, and, since we are both a little crazy, rebuilt the interior
while extending the cabin
a foot and a half to the stern.
I don't even want to think of the hours of work, but it was tolerable as it was spread out over six or seven years (I know, I know, its a long time to be without a boat). We both like to work on boats and putter around, which also helped.
Was it worth it? Considering that one forgets the hard work as time goes by, and will always have the beautiful result, YES, it was worth it. It helps a lot that this schooner is a rare and beautiful boat that is a lot of fun to sail.
So if the boat will be worth it, if you like to putter around with boats and if you have the time; go for it. Otherwise, I understand it is a buyer's market; you could go look at a few boats for sale
to help you answer the question of whether to continue fixing this one or buy another. Don't forget that buying
another boat may expose you to a whole new set of problems.