A couple of quick thoughts.
1) Have you tried Compact and Repair.
2) If you cannot do that, can you import selectively into two or more new databases, then compact and repair and, rejoin and continue from there?
Haven't got a db that size to try myself, but let me know how you get on as I can see one of mine getting to that size before too long and it would be useful to know the escape route in advance.
Best of luck
Tom