all of these things might help.
Personally i would like to add 2 more things.
Increase your FOV from 90 to say; 100-110 (console : /cg_fov 100)
Fov stands for field of view, and if you increase your FOV, you increase the angle of sight. To put it short : fov larger = see more happening in the corners of the screen.
This is especially helpfull when the enemy attacks you from the side. It allso allows you to try and circlestrafe (To strafe around the enemy in a circle while keeping your aim on him) around the enemy, preferably just outside his fov!
so : fov up, and circlestrafe.


