Well, 25 amps is not as bad as 30. I thought you just said you had a 30 amp controller.
In my opinion, it is pushing it a bit, to use that battery with more than a 20 amp controller. It would also depend on how you are riding it. You could be riding a route that never requires more than 12 amps, or you could be pulling 20 amps or more the whole way. Just depends on what your real world load is.
Knowing what your real world amps rate is, can be priceless. It's why we call a cycleanalyst a cheap investment. Knowing your watts or your amps helps a ton for knowing you have set up the bike correcty, for your controller, your motor, your battery, AND you riding it.
Since we still have more than one variable in play here, we can't definitely say much. But my guesstimate is that you have two problems, each from a different cause.
Fuse blowing, and hot fuse holder.
Chances are, you pull 25 amps just enough to get the fuse hot. The fuse holder also makes an imperfect connection, that causes resistance. So your fuse holder is actually causing heat to flow into the fuse itself. This resistance also means that if you draw 25 amps on the controller, plus you have 5 amps of resistance at the connection, including all the other connections on the bike, BINGO you now are drawing over 30 amps and the fuse blows as it is supposed to.
Battery shutdown without the fuse blowing.
This is different, you simply have emptied the battery and now the battery bms shuts off the battery. If you are drawing enough to blow that fuse, you are murdering the battery with high amps, and have been for awhile. The battery is not liking it, and will have lower capacity any time you draw amps out of it faster. Possibly, you have worn it out early.
One last question, was the battery and motor and controller sold to you as a complete kit? If so, by who? I could be wrong about your controller being too big. That is strictly my own opinion, and I am quite conservative about it because I happen to have a really big hill that I have to climb every day. I am not completely familiar with the specifications on your particular battery. But one thing we've learned here about battery size, it's good to double it.
Lowering the amps can be done a few different ways. One is to clip out one of the shunt resistors. But that's pretty drastic. Your motor and controller are a good match I think. It's just that you may have a battery that, in it's current condition, is not as able to stand it as when it was new.
THE LIPO RULES. NEVER ABOVE 4.3V NEVER BELOW 2.7V DON'T PUNCTURE
Ideal charging /discharging range for Lipo, 3.65v minimum 4.1v maximum
See battery technology section, FAQ thread at the top of the page for lipo noob info.