2D fps + moving the objects

I'm new in unity, and my english is bad, so sorry first of all

I'm making a 2D iOS game where the player moves to the right and the enemy comes from the right side of the screen. I've downloaded the demo version that has Fixed Timestep = 0,02 (50fps). The internet says i should make it 30 or 60fps for iOS. Well I changed that in my project to Fixed Timestep = 0,033 (30fps) and added:

Code (csharp):

1. int frameRate = 30;
2. public void Start () {  
3. Time.captureFramerate = frameRate;      
4. }

but the player and enemys started to move strange - they all stop periodically.

After that I read that if I use FixedUpdate () I don't need the frameRate - so I just deleted that. Now my player moves a bit snatchy and I just want some normal smooth. Here's how I move the player and enemy:

Code (csharp):

1.        
2. void FixedUpdate ()
3.         {
4.             if(rigidbody2D.velocity.x < maxSpeed)
5.                 rigidbody2D.AddForce(Vector2.right * current_moveForce);
6.    
7.             if(Mathf.Abs(rigidbody2D.velocity.x) > maxSpeed)
8.                         rigidbody2D.velocity = new Vector2(Mathf.Sign(rigidbody2D.velocity.x) * maxSpeed, rigidbody2D.velocity.y);
9.  

Whatever I do the objects still dont move smooth. Can anyone tell me what am I doing wrong?
ps: Im' trying to make the player and the enemy stop OnCollisionEnter2D, but they are pushing each other. As I understand the only way to fix that is to manage their mass, yes?

 

Fixed timestep is for physics, and has no effect on the visible framerate. Time.captureFramerate is only to be used for capturing video; do not use it in a released game because it makes it run as fast as possible.

--Eric