I can't fix your problem, but I can tell you that I was able to order a replacement tweeter directly from Monitor Audio for a very reasonable price when I had a similar issue. You didn't mention how old your speakers are.
Higher crossovers (120 - 150Hz) can work well if you use steeper low-pass filters (24 - 48 dB/octave) on your subs. This is assuming you have the equipment to measure and EQ. If not, then 80 Hz is the safer choice to avoid localization for a single sub. As others have mentioned, localization...