> lausir: (ll. 777): Gordon seem to suggest that somehow this is due

to them being hindered by saddle-packs, but surely it is just as
much the fact that at this stage the swamp is impeding Eyvind´s
party while Hrafnkel are still on solid ground.

I don't know, but you could be right. Jones just has "unhampered",
which I guess could be taken either way.

> Útan í (ll. 785): Does this mean beyond as Grace and Patricia have

or (sticking) out in as I have?

Jones has "on the slope of the mountain". A lot of the Google
quotes suggest the same. I notice that some of these seem to be not
at the very foot or base of the mountain but some way up the slope.
On the other hand, I also found a bible quote that does suggest "at
the foot of" or "on the lower slopes of".

þar er hjalli utan í fjallinu í um 400 m hæð
þegar þeir gistu í búðum utan í fjallinu
fannst ég hanga í lausu lofti utan í fjallinu
en það liggur hátt utan í fjallinu
Einnig er sérkennilegt að sjá græna slikju utan í fjallinu

Icelandic: annar helmingurinn utan í Garísímfjalli og hinn
helmingurinn utan í Ebalfjalli
Swedish: Den ena gruppen ställde sig vid foten av berget Gerissim
och den andra vid Ebal.

Half of the people stood in front of Mount Gerizim and half of them
in front of Mount Ebal.
Half of them stood in front of Mount Gerizim and half of them in
front of Mount Ebal.
half of them toward mount Gerizim, and the other half of them toward
mount Ebal
half of them over against Mount Gerizim and half of them over
against Mount Ebal
Joshua 8:33

> grjót (l. 789) Gordon and Zöega gloss this with a plural meaning

ie stones, even though it is gramatically singular. I guess there
must be some basis for this…

Yes, that's just how it's used, like the English collective
singular "gravel":

Ok er Gísli heyrði til, at grjótit sarglaði, mælti hann svá: "Maðr
ferr þar ofan ór hlíðinni ok heldr mikill, ok sá vill oss finna."
When Gisli heard the stones clattering he said, “There’s a big man
coming down the slope there to meet us."

Örninn flýgr hátt svá at fÅ"tr taka niðr grjótit ok urðir ok viðu
The eagle flies at such a hight that [Loki's] feet hit the stones
and gravel and trees

Á grjóti byggði hygginn maður hús.
The wise man built his house upon the rock.


Á baki létu blíkja,
barðir váru grjóti,
Sváfnis salnæfrar
seggir hyggjandi.

Cautious men made Odin's hall-roof-shingles [=shields] gleam on
their backs; they were pounded with stones. (Describing men running
away in battle.)