Random thoughts....
The whispers mention lots of people both dead and alive, some we know and some we don't.
I expect they're at least as ubiquitous as the Others, we just don't hear them all the time. Not sure we see the Others all the time either.....
I suspect the remote viewing takes place through selected animals on the island. In fact I'd argue the whisperers can remote control such animals. They don't want to be shot 'cause it'll cost them some expensive equipment and/or the Losties might discover said equipment while eating the animal (conjures up an interesting scene), and/or it might hurt the remoties if an animal they're connected to dies.
I'm thinkin' the plane crash remark is a captured memory from an earlier crash, maybe the drug plane. Here are all these new people. How'd they get here? Maybe the same as me! Yup, he's got the same dumb look I had just after my crash.
Once they absorb a person's memories they know as much or more about that person as the Others do. The Others know the second hand history, the things that appear in the public record, of, say, Kate. The Whisperers know her inner thoughts. The Others know what things say, the Whisperers know what things mean (think the Sheriff/Jack exchange). In our privileged stations as viewers, we get both, just reallllllllllllllly slowly..... Something like this came out in the Kate/Juliet exchange about Jack as well. Juliet knows all of Jack's history, so assumes Jack sent Kate and Sawyer away 'cause his heart was broken (again). Kate knows Jack from three months of living with the man under intense pressure and thinks Jack sent them away to protect them. Juliet knows his history, Kate knows him.