As a side note to anyone experimenting with the i2c baudrate, you don't have to set the baudrate via config.txt, which requires a reboot. You can do it at runtime by configuring the kernel module with modprobe:
sudo rmmod i2c_bcm2708
sudo modprobe i2c_bcm2708 baudrate=400000
Also bear in mind that Pi does not support clock stretching on I2C, so I2C devices ...
Most of what you have configured is not needed and may be part of the problem.
Don't add modules to /etc/modules, don't set the GPIO mode with raspi-gpio or similar, don't enable automatic load of I2C kernel at boot.
Remove everything you have done and just add the following line to /boot/config.txt.
Reboot and check that the device /dev/...