The test kit may or may not be accurate for FW
but just to be safe I'd get a FW
kit, the API Master kit is best.
You did dechlorinate the water prior to putting it into the tank, right?
Is there an air stone in the tank or is the filter causing surface agitation? The bacteria require oxygen so if your water is stagnant that could be a factor. You should be seeing an ammonia drop by now so something is off.
I'd do a 100% water change to restore buffers and minerals in the water (don't forget to dose dechlorinator prior to the water going into the tank) then redose ammonia (make sure you aren't overdosing as that can stall the cycle too) and try to get a FW
test kit and let's take it from there. You can also bump up your heat to 86 if your heater is adjustable.