ol3 load wfs layer Clusterversuch(funktioniert nicht)

HTML

<script src="http://cdnjs.cloudflare.com/ajax/libs/proj4js/2.2.1/proj4.js"></script>
<script src="http://epsg.io/3301.js"></script>
<script src="http://code.jquery.com/jquery-1.11.0.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/ol3/4.6.5/ol.js"></script>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/ol3/4.6.5/ol.css">
<div id="map" class="map"></div>

JavaScript

var projection = ol.proj.get('EPSG:3301');
 window.projection = projection;
 projection.setExtent([350000, 6370000, 750000, 6630000]);
 var base = new ol.layer.Image({
     title: "Maa-ameti aluskaardid",
     maxResolution: 10000,
     source: new ol.source.ImageWMS({
         url: 'http://kaart.maaamet.ee/wms/alus?',
         ratio: 1.05,
         params: {
             LAYERS: 'MA-ALUS',
             FORMAT: 'image/png',
             TRANSPARENT: 'false',
             VERSION: '1.1.1'
         }
     })
 });
 var vectorSource = new ol.source.ServerVector({
     format: new ol.format.GeoJSON(),
     loader: function (extent, resolution, projection) {
         var url = 'http://loom-gis.geo.ut.ee:8080/geoserver/ermas/ows?service=WFS&' +
             'version=1.1.0&request=GetFeature&typeName=ermas:testdata_geopnt&' +
             'outputFormat=text/javascript&format_options=callback:loadFeatures&' +
             'srsname=EPSG:3301&bbox=' + extent.join(',') + ',EPSG:3301'

         $.ajax({
             url: url,
             dataType: 'jsonp'
         });
     },
     strategy: ol.loadingstrategy.createTile(new ol.tilegrid.XYZ({
         maxZoom: 19
     })),
     projection: 'EPSG:3301'
 });

 window.vectorSource = vectorSource;
 var defaultStyle = new ol.style.Style({
     image: new ol.style.Circle({
         radius: 3,
         //                fill: new ol.style.Fill({color: '#AA0000'}),
         stroke: new ol.style.Stroke({
             color: 'red',
             width: 1
         })
     })
 })
 var testdata_geopnt = new ol.layer.Vector({
     source: vectorSource,
     style: defaultStyle
 });
 window.testdata_geopnt = testdata_geopnt;

 var clusterSource = new ol.source.Cluster({
     distance: 40,
     source: vectorSource
 });
 var loadFeatures = function (response) {
     vectorSource.addFeatures(vectorSource.readFeatures(response));
 };
 window.loadFeatures = loadFeatures;



 var styleCache = {};
 var clusters = new ol.layer.Vector({
     source:...