> Brá hann því jafnan undir fót sér.

> He constantly thrust that under each foot.

> He always turned it under his foot (to straighten it –
> according to M&P).

Remember, this wasn't his good sword. From what I've read,
this description is quite believable.

> Þá féll Án og hafði hann þó barist um hríð svo að úti lágu
> iðrin.

> Then An fell; and he had nevertheless fought for a while
> so that the (i.e., "his") bowels lay out

> Then An fell and he had still fought on?? for a time so
> that (his) entrails lay outside.

Here <svo að> should be understood as 'in such a condition
that', not 'in order that' or 'so that as a result'. It's
saying that even though his entrails were exposed, he kept
on fighting for a while.

> Í þessi svipan hjó Kjartan fót af Guðlaugi fyrir ofan kné
> og var honum sá áverki ærinn til bana.

> In this moment, Kjartan hewed the foot off Gudlaugi below
> the knee and it was to him that would sufficient to kill
> (him).

> In this fight Kjartan hewed Gudlaug’s leg off above (the)
> knee and that misdeed was sufficient for him to (cause
> his) death.

This is <svipan> Z3: 'At this moment', i.e., the moment when
Án fell.

> Þá sækja þeir Ósvífurssynir fjórir Kjartan og varðist hann
> svo hraustlega að hvergi fór hann á hæl fyrir þeim.

> Then they, the four sons of Osvifr, sought Kjartan and he
> defended himself so valiantly that each of them retreated
> before him. (Z. hæll - hopa (fara) á hæl fyrir e-m, to
> retreat, recede before one)

> Then those four Osvif’s sons attack Kjartan he defended
> himself so valiantly that neither did he retreat before
> them.

This is <hvergi> adv. Z2 'by no means, not at all': 'so
valiantly that he did not give an inch before them'.

> Og er þér nú það vænst að veita öðrum hvorum og reyna nú
> hversu Fótbítur dugi."

> And when you now expected that, to help from time to time
> and try now how Foot-biter does good service."

> And when you now expect it that to grant to which (or)
> other (whichever side) to prove now how Foot biter
> serves.”

Here <er> is the verb 'is', and <vænst> is the superlative
of the adjective <vænn> 'fine, promising'. For <öðrum
hvorum> see <annarr hvárr>; it's the dative plural of ON
nom. plur. <aðrir hvárir> 'one or the other (of two)'. 'And
it is now most promising to you [i.e., best for you] to help
one [side] or the other and test now how Legbiter serves.'

> Og er Óspakur sá að þeir mundu eigi bera af Kjartani þá
> eggjar hann Bolla á alla vega, kvað hann eigi mundu vilja
> vita þá skömm eftir sér að hafa heitið þeim vígsgangi og
> veita nú ekki "og var Kjartan oss þá þungur í skiptum er
> vér höfðum eigi jafnstórt til gert.

> And when Ospakr saw that they would not surpass Kjartan,
> then he eggs Bolli in every way, told him would not want
> to know then disgrace for himself later to have promised
> to back them in battle and not help now "

> And when Ospak saw that they would not overcome Kjartan
> then he urges Bolli in every way, said he would not want
> to know that shame after himself to have promised them
> backing in a battle and now not granting (it) “and Kjartan
> was then for us difficult in dealing when we had not done
> equally severe (things) to (him).

Rob: <þá> in <þá skömm> is the acc. sing. of the
demonstrative pronoun <sú> 'that', as Grace has it. But I
prefer your reading 'to help' for <veita>.

> Og ef Kjartan skal nú undan rekast þá mun þér Bolli svo
> sem oss skammt til afarkosta."

> And if Kjartan shall now escape then then you, Bolli, will
> (be) so as (for) us close to hard terms." (Z. reka 9 -
> rekast undan, to escape)

> And if Kjartan shall now escape then you, Bolli, will such
> as us scarcely (escape) hard terms.

If I'm not mistaken, there's an understood <vera> after
<Bolli>: 'then to you, Bolli, as to us, will very soon be
hard terms'. (<Skammt> appears to refer to time here.)

> Þá mælti Kjartan til Bolla: "Víst ætlar þú nú frændi
> níðingsverk að gera ...

> Then Kjartan said to Bolli: "Certainly you now intend,
> kinsman, a dastardly deed to do ...

> Then Kjartan spoke to Bolli, “Certainly now you
> anticipate, kinsman, to do dastardly work, ...

I'd go with 'intend'.

> Síðan kastaði Kjartan vopnum og vildi þá eigi verja sig en
> þó var hann lítt sár en ákaflega vígmóður.

> Then Kjartan threw (down his) weapons and wanted then to
> not defend himself although he was little wounded and a
> vehement warrior.

> Afterwards Kjartan cast down (his) weapons and then did
> not want to defend himself but still he was lightly
> wounded but very exhausted from battle.

Rob: <vígmóðr> 'weary in battle', literally 'battle-weary'.

Brian