low fps when looking in a direction with many objects

That's normal, because the render engine is rendering everything the camera faces, even if the objects are behind something. With Unity Pro you can setup Occlusion Culling which calculates at runtime wether objects are seen by the camera. I have only the free version, so I made my own "fake occlusion culling". The script is below. Use: make a new gameobject and drag all other objects that causes the framedropping into this gameobject als childs. Now attach the script on the gameobject. If you haven't any important script on your objects you want to cul, then don't check the "soft culling" checkbox, this would deactivate the objects in the distance. If you check this option, only the renderer components on the objects get deactivated in the distance.

 var culRange : int = 100;
 var softCulling : boolean = false;
 
 function OnEnable() {
     for(var toCul : Transform in transform) { //get all objects we want to cul. Place them as childs of the gamobject that's script is attched
         TurnOnOff(toCul, false);
         CheckRange(toCul, 0);
     }
 }
 
 function CheckRange(toCul : Transform, waitFor : int) : IEnumerator {
     yield WaitForSeconds(waitFor);
     var curRange : int = Vector3.Distance(Camera.main.transform.position, toCul.position); //range from the camera to the object
     if (curRange < culRange) { //if in range acivate/make visible
         TurnOnOff(toCul, true);
     } else { //out of range -> deactivate/invisible
         TurnOnOff(toCul, false);
     }
     var checkIn = Mathf.Max(0.5, 5*curRange/culRange); //the next check depends on the range from the camera to the object (for better performance)
     //print("Check for " + toCul.name + " in " + checkIn + " seconds."); //for debug
     CheckRange(toCul, checkIn);
 }
 
 function TurnOnOff(toCul : Transform, state : boolean) {
     if (!softCulling) {
         toCul.gameObject.SetActive(state); //deactivate the object(s)
     } else {
         for (var r : Renderer in toCul.GetComponentsInChildren(Renderer)) {
               r.enabled = state; //make the object(s) invisible
         }
     }
 }
 
 function OnDrawGizmosSelected () { //draw a debug sphere to visualize the culRange, not needed for functionality
     Gizmos.color = Color.yellow;
     for(var toCul : Transform in transform) {
          Gizmos.DrawWireSphere(toCul.position, culRange);
     }
 }