Problem loading level layout from file in Breakout clone

I'm working on a Breakout clone and I decide to use files as method to load level layouts. The file is something like this:

N,N,N,N,N

N,N,N

N,N,N

Only indicates what type of brick I'll instantiate, the initial positions to set this are in the WallBuilder.cs shown next. But I got a problem when I use my script, because the bricks doesn't appear in the rights position, they look moved and translated, and in the start moment, they move, but I don't understand why, I leave you a screenshot of the game when starts:

And the configuration of the prefabs of my brick:

Also, I leave you the WallBuilder.cs, which constructs the level based on the size of the screen and puts each brick next to each other:

using UnityEngine;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.IO;

public class WallBuilder : MonoBehaviour
{
    public float xOffset = 0.31f;
    public float yOffset = 0.15f;
    public GameObject level;
    private List<List<string>> filedata;
    private Dictionary<string, string> prefabMap;

    // Use this for initialization 24
    void Awake ()
    {
        readFile("./Assets/" + Application.loadedLevelName + ".lyt");
        initPrefabMap();
        placeBricks();
    }

    // Update is called once per frame
    void Update ()
    {

    }

    private void initPrefabMap()
    {
        prefabMap = new Dictionary<string, string>();
        prefabMap.Add("F","FastBallsBrick");
        prefabMap.Add("I", "InverseBrick");
        prefabMap.Add("M", "MultipleBallsBrick");
        prefabMap.Add("U", "NonDestroyableBrick");
        prefabMap.Add("N", "NormalBrickPrefab");
        prefabMap.Add("S", "SlowBallsBrick");
        prefabMap.Add("X", "XResBrickPrefab");
        prefabMap.Add("XX", "XXResBrickPrefab");
    }

    private void readFile(string filename)
    {
        TextAsset sr = Resources.Load("Level2") as TextAsset;
        filedata = sr.text.Split('\n').Select(s=>s.Split(',').ToList()).ToList();
    }

    private void placeBricks()
    {
        Camera mainCamera = tk2dCamera.Instance.ScreenCamera;

        float halfWidth = mainCamera.aspect * (mainCamera.orthographicSize/100);
        float tempYOffset = (mainCamera.orthographicSize/100) - yOffset - 0.5f;
        foreach (var data in filedata)
        {
            float tempXOffset = -halfWidth + xOffset;
            foreach (var item in data)
            {
                if (tempXOffset < halfWidth - xOffset)
                {
                    instantiateBrick(item,tempXOffset, tempYOffset);
                }
                else
                {
                    break;
                }
                tempXOffset += xOffset;
            }
            tempYOffset -= yOffset;
        }
    }

    private void instantiateBrick(string type,float xOffset,float yOffset)
    {
        string item = type.Trim ();
        if (prefabMap.ContainsKey (item)) {
            GameObject.Instantiate (Resources.Load (prefabMap [item]), new Vector3 (xOffset, yOffset, 0), Quaternion.identity);
        }
    }
}

Also, I leave you the collision exit method of the brick, just in case:

   void OnCollisionExit2D(Collision2D collision)
    {
        if (collision.gameObject.tag == "Player") {
            brick.addHits ();
            if (brick.getCurrentHits () == brick.getNeededHits ()) {

                Brick.ObjectBrick objectBrick = brick.getObject();

                if (objectBrick != Brick.ObjectBrick.NONE) {
                    String objectBrickStr = StringUtils.GetStringValue(objectBrick);
                    Instantiate(Resources.Load(objectBrickStr), gameObject.transform.position, gameObject.transform.rotation);
                }

                int totalPoints = brick.getPoints()*brick.getCurrentHits();

                GameObject gameObjectGM = GameObject.Find("GameManager");
                GameManager gameManager = (GameManager) gameObjectGM.GetComponent(typeof(GameManager));
                gameManager.addScore(totalPoints);
                gameManager.minusBrick();

                Destroy(gameObject);
            }
        }
    }

I have tried different things:

1. I harcoded the positions for the blocks, but after the Instantiate method in the WallBuilder.cs, they are set in other positions, maybe I'm wrong, but could be something about physics between the objects.

2. After that I removed the rigidbody2D of the prefab bricks, and they start to overlap each other no matter the offset I defined in the WallBuilder.cs. (I'll upload a screenshot of this later).

3. After those tests I notice that this problem doesn't occur when each row of my level has the exact amount of bricks, if I add one in any row, that problem occurs when I start the game.

I hope someone help me out.

Thank you