Pleasure. Note your user name, why are you an unhappy snapper? Or has that changed since getting a Pentax?

If you're using prime lenses you don't have much choice, it's when you need a different focal length lens on wherever you happen to be. You can't pop home from a vacation to swap lenses between shots in your special dust free lab!
Providing you're careful it isn't in reality much of an issue. Obviously avoid a sandy beach on a windy day or a dusty environment. I've seen many SLRs and DSLRs sitting without lenses or body caps on at camera fayres and in shops. Not ideal maybe but it shouldn't be a problem just to swap over a lens when you need to wherever you are (within reason.).

For auto focus both switches need to be on AF. If either or both are on MF that's what you'll get.
If you use back button focussing rather than the shutter release focussing you get the best of both worlds. The lens will focus when you press the rear AF button, but will not try again when you press the shutter release so you don't have to wait while it tries to focus yet again. Might not be ideal for every subject but often works the best, though might need a bit of getting used to.
I've been trying to think of any instances where back button focussing may not be ideal. I'm still thinking... nothing's come to mind so far!

All I can say is the 10 miles was purely a guess, but I'm pretty used to estimating distances right back to my Boy Scout days and private flying from and around Biggin Hill and Stapleford Tawny.
Regarding the photo, I'm quite surprised how much detail can be made out from so far away. It says quite a lot for Pentax's shake reduction system and the DA*300mm lens as the camera was hand held, albeit steadied on a fence to help, and that was with an entry level camera (the K-S1.) I boosted the image contrast in EasyHDR3.

That has crossed my mind but one hears 'scientists' on the radio and TV saying it is a definite amount each year with statements such as, "The result is that the Moon is being pushed away from Earth by 1.6 inches (4 centimetres) per year and our planet's rotation is slowing."
No mention of elliptical orbits ! However, if the basis for that is correct, the metre you suggest is only two decades away. I wonder how much cameras will evolve in that timescale.
Interesting quote here: http://www.universetoday.com/112450/why-is-the-moon-leaving-us/
"The moon is moving away because it is sick of the blue & green colors of Earth."

Yes, Adobe certainly does. I think part of the problem is that manufacturers aren't consistent in the use of some of the the fields meaning they cannot be described/identified accurately.
Discussed here: http://stackoverflow.com/questions/1320881/exif-key-names-explanations

Google was my friend (other search engines are available!)
Half is the operative word there. Still trying to find the rest!

For Vic. From the AIS chart I've calculated the ship was approx 8 nautical miles off the coast (that's around 9 normal miles.) Reckon my 10 miles away from home was a pretty close estimate!
What do you think?

One thing I find odd is that we're told the moon is gradually getting further away from the earth, yet here it is closer than it has been for many decades.

I find saving as tiff causes loss of exif, even if subsequently reimported then resaved as a jpeg. Some editing programs have an option whether to save the exif or not, so may only require a tick in a box somewhere.
Just don't use save for web if you want to keep the exif intact. If it's to upload here, resize to 1000 pixels and just do a normal jpeg save.
Most web sites now have their own server software to resize/make the image suitable (often ImageMagik) so not much to be gained from 'save for web' anymore. It's now just considered a legacy option and treated as such in recent PhotoShop editions.