Considering your water temperature is 75/76F, your pH is 7.5 and your measured ammonia is 0.1, your NH3 (unionized toxic ammonia), by my calculations would be about 0.002 mg/l.
Considering your test kits ability (tolerance), even a high end reading of, 78/7.8/0.25 would only calculate to a 0.009 NH3 concentration. Both below levels toxic to most fish (0.05 mg/l). However, this is only a snapshot in time.
Unfortunately you cannot measure Dissolved Oxygen, which would be another wildcard in your water quality. Are your fish lethargic? Laying on the pond bottom with clamped fins, or gasping at the water surface?
You can take a fresh dead fish and look for gill color and blood color. Red/Lavender gills may indicate high NH3 and brown blood would indicate high nitrates. Also, fraying of the fins, which I see in your last photo is a sign of high ammonia.
