I cant see too much in your smart images, so cant see what you try to do, but...
If you like to use tile based map and this map is fix, so not change in runtime, better if you create an empty gameobject and add a box collider component on to this empty gameobject and resize this collider size on to the map tile group.
So better if you use just one collider for a group of tiles.
Separate the graphics and colliders.
With this you also can get some plus speed for the game what is maybe not important at now, but if you like to make larger maps, it will be good.