If it is leaking in that many places, you might be better off with a replacement. As already mentioned, look for some type of architectural salvage store, preferably as close to you as possible. And make sure if you do buy a used replacement that it has been tested.
Between the weight, repair issues, and trying to find a replacement, you might be better off finding a heating guy who knows old systems and can advise regarding repair/repace. They would probably have sources for replacements as well. That's what I ended up doing with the old system in my 1910 home.
Best of luck!
That's just my opinion. But it's free, so take it for what it's worth to you.