At the very least I would recommend you send your reciever in for a check-up. After soooo many hard landings and what appears to be a terrible ending to your edge, I would have to suspect the reciever.

Secondly, you can obtain a voltage meter for minimal money that will give you an honest readout under the load of the plane which installs in the plane. Servos that have taken a hit are sometimes working well but inducing a substantial load on the battery while doing so. An indication of this is louder noise.

Finally, Bell cranks do work well but are old technology. A better solution might be to install a pull-pull on your elevator. An excellent example of this is in the Dave Patrick Ultimate review that is in the magazine section of RCU. The Katana that you are building is notorious for coming out tail heavy with OS 2 strokes so I would be careful if I were you in building it. The design is more aerobatic then most edges so therefore much less tolerant of errors.

As always, these are only my opinions, they may not be worth the electric it took you to read them.