Not sure.

Yes. I have had Deathclaws attack one of the swamp settlements by the glowing sea area.

Edit: Murk Water Construction Site.

Had a glowing deathclaw once, though it was only 1, and my fence just confused it.

They should pretty much always travel in packs. Cannot wait till the GECK so I can mod it so that JUST surviving in a journey from Sanctuary to Lexington is an accomplishment, even on "Normal" difficulty!

Yes, I know, there are other tools to change the files, but I do not want to use anything that will create problems or work down the road, which I fear a lot of the current mods will do eventually.

Yes. I started building walls around the perimeter of my settlements after I saw a deathclaw kill almost everyone in Abernathy Farm.