> Það lagði hann til að vér skyldum öllu kyrru (kyrra, n or kyrr, adj as adverb?) fyrir halda

Neuter adjective acting adverbially, I think. That would agree with the adjective `öllu'. CV lists the idiom under the heading of the adjective `kyrr': `halda kyrru fyrir' "not to stir", also `halda á vápni kyrru' "to hold a weapon at rest" (Grágás ii. 64).

> Kemrat, Ullr, um alla,

álmsíma, mér grímu,
beðhlíðar man ek beiði
bauga, svefn á augu,
síz brandviðir brenndu
böðvar nausts á hausti,
ek em at mínu meini
minnigr, Níal inni.

"All through the night, sleep does not come to me; I recall the fighter. Since shield-warriors burnt Njáll in his house in autumn, I am mindful of my hurt."

`álm-síma' "bowstring" (literally elm-string, from the name of the tree whose wood was used to make the bow). Words like this are listed in Lexicon Poeticum under the equivalent short vowel, thus `almsíma', which is a more archaic form. Short back vowels were lengthened in Iceland around 1200 before certain consonant clusters, namely /l/ followed by a velar or labial consonant, /f/, /p/, /m/, or /k/, /g/, and sometimes /s/ or /n/ (hálfr, álmr, málmr, úlfr, gólf, dálkr, fólginn, háls, etc.), compare `alin', `öln' "ell" with the genitive `álnar', which occurs besides analogical `alnar'. (Gordon: An Introduction to Old Norse, § 54, Noreen: Altisländische und altnorwegische Grammatik, § 120.3 [ http://lexicon.ff.cuni.cz/png/oi_noreen/b0092.png ].)

`gríma' "night" (a `heiti', poetic name, for night; literally "mask", from the idea of darkness as a mask that hides things from sight; cf. Old English `niht-helm' "night-helm, the cover of darkness").

`beð-hlíð bauga' "shield" (decorated with rings; literally "bed-shield of rings", an explanatory expansion of the basic kenning `beðr bauga' "bed of rings" = shield).

`beiðir beð-hlíð bauga' "wisher/demander/enforcer of shield" = "warrior/man".

`naust böð' "shield" (literally "boathouse of battle").

`brand-viðir nausts böðvar' "warriors" (literally "sword-trees of shield"; this make a normal kind of kenning for warriors, according to the convention by which a man or woman is refered to as a tree of some accoutrement associated with their gender, but presumably not accidental that `brandr' also means "firebrand").