You have interesting information and beliefs.
Let me address your points.
The dead often TRY to communicate with the living but the living aren't listening on the right frequency. Don't blame the dead people. I personally have encountered a few murder victims who tell me about their murders. But I'm a professional. most people don't have their "radios" even on let alone tuned in to the right channel.
Deceased people often are comforting their living parents or children. You betcha. Again, most living people can't detect them. Don't blame the dead people.
Your third point is interesting. I know of a few cases where pre-arrangements were made and were completed but you probably would not have heard of these. Also, the deceased may not be able to make good on their promise due to free will, the rules of the game, or a host of other reasons. And when a deceased person comes through with validating evidence a lot of people realize they are really there.
Dead people DO warn the living of imminent danger. Again, most people can't hear or see or detect the dead. They're on a different frequency. It would be like trying to hear channel 5 while you're tuned to channel 10. Whose fault is it if you're on the wrong channel?
If you're really interested in knowing more about the afterlife, study it a little. Plenty of info out there.
good questions though!