Bearding is usually from heat. In your case, I am somewhat reassured, as it means that your hive has a big enough population to need to beard.
The fighting is a concern - suggests robbing. The bee that you showed which is blacker than yours is evidence, but not for the reason you might think. The yellow colour on the abdomens of most bees is in the hairs which coat the surface. When bees fight, those hairs get broken off, showing the black chitin underneath. Much like a pale-furred dog may have black skin under the fur. If you have robbing, you definitely need to reduce the entrance. It is likely that the “expert’s” honey spill probably enticed the robbers too - bees can smell honey quite a distance away.
Inspections can also make robbing worse, so I would not inspect unless you have to. For your hive, I would think once every 2 weeks would be enough.
Finally, if the robbing doesn’t stop in a day or two, or it gets worse, you may need to consider a robbing screen or other methods for discouraging the marauders. You can use the Forum search tool for lots of tips. Guard bees tend to be young bees, so that may be why you are seeing dead small bees outside - perhaps they died defending the hive.