2 - I bought arms torque, weld them and carefully installed on the bicycle. I also change the controller from the KU123 to KU93, which provides less power to motor and so less torque.
3 - I tested again with the arm torque:
Here is the bicycle with the arms torque:
The arm torque seems very strong however I decided to make some tests before ride the bicycle. I were afraid that dropouts broke again. Please see the following video to see the simple tests I did, by trying to simulate going at high speed and do a jump because of some bump (I were pushing the handlebars of the bicycle to the ground, to try block the wheel):
And one dropout broke with the tests:
The BMSBattery torque arms are very strong but they may had slipped a bit because the fixation to the fork may not be perfect. As dogman told and I agree:
dogman wrote:(...) I would not be a bit suprised if my forks would fail that test too. That bump test is pretty harsh. It simulates the torque you'd have if you landed a jump with the brakes locked. Landing a jump, the wheel would not try to stop so hard normally, it would just keep rolling.