Assuming you're on MSFS 2020, and everything is installed correctly, I think all of your remarks can be attributed to the complexity of the aircraft. Are you familiar with the triple-fed bus system, and turboprop engine limitations?
There are many configuration issues that could cause what you're seeing. For instance, many of the aircraft lights will not work unless the left and right generator buses are online. You will also have to disengage the starters manually for the starter-generators to produce power (usually what closes those bus ties). If it's just the electronics that shut down after several minutes, that comports with the generators not being online too, since the battery will eventually give out, or overheat. If it's the engines that shut down after a few minutes, you are probably exceeding the engine's torque or ITT limits.
Long story short: The current version of the Analog King Air has been in the hands of thousands of happy users for a couple years now, so these are almost certainly not bugs. There could be an installation issue, or an incompatible freeware addon, but most likely it's just the learning curve required for one of the most complex general aviation aircraft in service.
If you continue to have questions, I am always here to help! Feel free to share any videos or screenshots of your situation too. Helping people learn complex systems is my favorite part of creating these aircraft, so I'm always to take a look.
