so this place has been over-discussing the fh and ignoring everything else... yours is a good evidence for that.
fh is your best shot, slightly more accurate footwork and more relaxed racket drop will help... but you hit it good.
bh - the closed stance 2hbh is supposed to hit off the front foot... you have weight shift problem there... you are spinning out and falling backwards.
slice - you chop at the ball with no target in mind... you have to set the racket face, at top of the backswing, at the exact angle you want to make contact at, then cut down and push forward at the same time, while maintaining the same angle.
volley - wrong grip and too much slapping at the ball.... needs rework.