If you encounter issues/bug, please open a specific bug report.
From the description/sound of it, your issues are not related to the current issue, so please consider filling a proper bug report.
The Xbox360 controller is actually the one advised as mentioned in the Gamepad manual article.
Always read the manual first.
Also, for me, in firefox AND chrome it is not possible to control only the verticality of the movement. But in my opinion this is actually due to the fact you are using "0" as a limit in your events, not allowing for a deadzone in the usage of the pad.
So if I move slightly/barely my stick towards the right or left, the target will move in that direction nonetheless.
See this example using a deadzone and having a more acceptable movement/feeling in Chrome and FireFox alike.
(using a XBox 360 controller to test with other standard USB but it should be fine nonetheless)