Here’s my translation

Alan

Sverðit kom í vindásinn ok stökk sundr í miðju. 
The-sword came into the-windlass and (it, ie the windlass) flew asunder in (the) middle.

Hrærekr hjó á móti. 
Hroerekr hewed in return.

Bósi snerist undan á hæli. 
Bósi drew back immediately (cf fara aptr a hæli, Z, lit: on (his) heel -or, perhaps,  could be interpreted literally?)

Sverðit slapp af hjálminum ok niðr á herðarnar ok reif af honum alla brynjuna, ok fekk hann sár á herðablöðunum, ok gekk svá niðr um allt bakit, at öll klæðin rifnuðu af honum, svá at hann var nakinn allr eftir, ok af vinstra fæti hælbeinit. 
The-sword slipped off the-helmet and down on-to the-shoulders and tore all the-coat-of-mail from him, and he got a wound on the-shoulder-blades, and (it) went down along the-whole-back in-such-a-way, that all the-clothes were-torn from him, so that he was all naked afterwards, and the-heelbone (torn) from (the) left foot.

Bósi þreif upp ás einn, en Hrærekr vildi þá hlaupa fyrir borð. 
Bósi took up a single large pole (sail yard), but (and) Hroerekr wanted then to leap over-board.

Bósi sló hann í sundr við hástokkinum, svá at sér fell hvárr hluturinn. 
Bósi struck him asunder (ie in two) against (við, Zi.1) the-gunwale, so that each-part (of-the two) of him (ie both his sundered parts) fell.

Var nú ok fallinn mestr hluti liðs þeira, en þeir þágu grið, sem eftir lifðu.
The greatest part of their troop was now also fallen (in battle), but (and) those, who lived after (ie survived), accepted a truce.

Þeir kanna nú lið sitt, ok var eigi eftir meir en hundrað manns liðfært, ok áttu þeir fóstbræðr nú miklum sigri at hrósa. 
They muster now their troops, and not more than a hundred able-bodied men (persons) (gram sg) were left (vera eptir), and those foster-brothers now had-the-right (eiga, Z4?) to triumph greatly (lit: praise a great victory).

Skiptu menn nú herfangi, en þeir váru græddir, sem græðandi váru.
(The) men now divided (the) booty, but (and) those were healed, who were (in need of?) healing.

16. Herrauðr ok Bósi settust at ríkjum.
16. Herauðr and Bósi settle in (their) kingdoms.

Síðan bjuggust þeir við brúðlaupum sínum Herrauðr ok Bósi, ok skorti nú eigi tilföng bæði nóg ok góð, ok stóð veizlan mánuð, ok váru menn með virðuligum gjöfum á burt leystir. 
After-that they, Herrauðr and Bósi, readied-themselves for their weddings (plural), and now (they) lacked not means (supplies), both sufficient and good, and the-feast lasted (lit: stood) a month, and folk were sent away with fine gifts.

Tók Herrauðr þá konungsnafn yfir öllum þeim ríkjum, sem faðir hans hafði stýrt.
Herrauðr took then (the) title-of-king over all those realms (plural), which his father had ruled.

Litlu síðar söfnuðu þeir liði ok fóru til Bjarmalands, ok beiddi Bósi sér þar viðtöku ok taldi þat til, at Edda ætti land allt eftir föður sinn, er nú var orðin eiginkona hans, ok segist hann svá helzt mega bæta landsmönnum þann mannskaða, sem þeir höfðu af honum fengit, at vera konungr yfir þeim ok styrkja þá með lögum ok réttarbótum. 
A little later, they assembled troops and journeyed to Bjarmaland, and Bósi requested acceptance (as king) for himself there and counted that towards (it) (ie argued his case by claiming), that Edda owned all that land after (ie as inheritance from) her father, who (Edda, not her father) now was (had) become his own-wife, and he says-for-himself so best (ie it to be so much better), (in order) to be able to compensate (the) land’s-inhabitants for that loss-of-life, which they had received from him, (for him) to be king over them and to assist them with (the) law and bettering-their-conditions. (Not sure that I got the grammar 100% right but I think I got the sense of it)

Ok með því at þeir váru höfðingjalausir, þá sá þeir engan sinn kost vænna en taka hann sér til konungs. 
And with that (ie because), that they were chiefless, then they saw at no time (ie there never would be) a better opportunity (choice) than to take him as king for themselves.

Var Edda þeim kunnig áðr at öllum góðum siðum. 
Edda was known (kunnigr) to them already in respect of all good (moral) conduct (gram plural).

Gerðist Bósi nú konungr yfir Bjarmalandi.
Bósi was-made (ie became) now king over Bjarmaland.

Hann átti son við frillu sinni, þeiri er hann herti jarlinn hjá. 
He had a son by his lover, that-one (ie she, the first farmer´s daughter) with whom he (Bósi) hardened (tempered, herða) the-“earl”.

Sá hét Sviði inn sókndjarfi; hann var faðir Vilmundar viðutan.
That-one (ie he) was-called Sviði the valiant; he was father of Vilmundr (the) Absent-minded (distracted, MnI).