1) When possible attach to the anchor with something more dynamic than a sling (climbing rope works wonders here)
not really sure I believe that 1 meter or less of climbing rope is all that much more dynamic than a sling, dyneema or otherwise. maybe the knot might make it more so tho...
Your average 10mm climbing rope has about 10% static elongation.
Your average nylon sling has less than 1% static elongation.
Your average dynex/dynema sling is basically steel.
So if you compare a 24 inch tie-in;
The rope will stretch 2.4 inches from static loading, but roughly three times that amount
under extreme dynamic loading (7.2 inches)
The nylon sling will only stretch 2.4 inches if dynamically loaded. The dynex will not stretch at all (zero energy absorption).
I'm not saying you shouldn't attach with a nylon sling, though I think you could easily make the argument you should not attach with dynex.
Another consideration is simply how much more edge/cut resistant the rope is than a nylon sling. (Think unexpected rockfall hitting anchor).
Bottom line, unless you are rappelling there is little reason not to use the rope to attach to the anchor.