Here’s my translation

Alan

Brestr þá upp þilit at baki þeim. 
The-board-partition (panelling) then breaks up at their back (ie behind them)

Koma þar fram tólf þrælar. 
Twelve thralls come forth there.

Þeir höfðu sviga í höndum ok járnsvipur. 
They had switches in (their) hands and iron-whips.

Létu síðan ganga á honum, en hann var í línklæðum einum, ok markaði því skjótt fyrir hverju höggi, en hann hafði ekki at verjast með nema knefana. 
(They) caused then to go at (ie attack) him, but he was in linen-raiment (night-dress) only, and (it) marked therefore speedily for (ie as a result of) each blow (ie each blow quickly left a mark on him), but (and) he had nothing to defend-himself with besides the-(his) fists (hnefi).

Náði hann þá einum at fótunum, ok þar með drap hann þrjá, en sá þóttist þó illa leikinn sem hann helt á.
He then got-hold-of one (ná + dative) (of the thralls) around (at, Z.i.6) the-feet, and there-with (ie in this way) he killed three, but (and) that-one (ie the thrall) whom he (ie Sigrgarðr) held on to (ie by the feet) bethought-himself ill-treated (leika, Z5) nevertheless (ie it wasn´t much fun for him either).

En því næst kváðu við lúðrar, ok var þá upp slegin hurðin. 
But (And) in that next (instant) trumpets (nominative plural) sounded (kveða við, Z3), and the door was then struck up (slá upp = bresta upp? hammered down, broken up? )

Váru þar þá komnir menn drottningar með alvæpni, ok sóttu þegar at honum. 
(The) persons (men) of the-queen were (had) then come there with all-weaponry (ie fully-armed), and at-once sought him out (ie attacked him)

Hann greip til þess sem fyrstr gekk ok náði í hjálminn ok snaraði þann úr hálsliðunum. 
He seized that-one (ie him) who went first and reached into the-helmet and twisted that (þann, masc, ie the helmet, presumably inclusive of head) out-of (the) neck-joint.

Hann sló annan með hjálminum til bana. 
He struck the next-one (ie thrall) with the-helmet (presumably still with head inside) until death.

Fekk hann þá sverð hans. 
He then got his (ie the thrall whom he had just killed) sword

Síðan ruddi hann sér götu til dyranna. 
After-that he cleared himself a path to the-doorway.

Hafði hann þá drepit þrítugra manna. 
He had then (ie by that time) killed thirty persons (men).

Var hann þá ákafliga móðr. 
He was then (ie by that time) exceedingly weary.

Fengit hafði hann þá fimmtán sár.
He had then obtained (received) fifteen wounds.

Váru þar þá komnir menn hans ok urðu fegnir er þeir fundu hann með lífi. 
His (own) people (men) were (had) then (ie by that time) come there and became (ie were) glad when they found him with life (ie alive)

Var þá sótt at þeim öllu megin, en þeir létu hefjast undan, ok er komust svá til skipa sinna. 
(It) was then sought at them (ie they were attacked) from all sides, but (and) they caused to draw-themselves back, and (er, what´s it doing here?) made-their-way thus to their ships.

Sigrgarðr var þá óvígr en meykonungrinn hafði dregið saman svá mikinn her, at þeir náðu hvergi landgöngu. 
Sigrgarðr was then unable-to-fight but (and) the-maiden-king had drawn together such a great army, that they (ie Sigrgarðr and co) obtained nowhere (hvergi) a disembarking (ie could find no place to land).

Sigldi Sigrgarðr þá heim til Garðaríkis, ok segir sínar ei sléttar. 
Sigrgarðr sailed then home to Garðaríki, and says his (journey, farar understood or scribal omission?) not smooth (ie didn´t go totally according to plan, understatement for abject failure)

Faðir hans segir honum slíks þaðan ván.
His father says to him (the, ie his own) expectation of such (genitive) (an outcome) from-that.

7.
7.

Nú bað Sigrgarðr föður sinn at fá sér lið at hefna sinnar svívirðingar, en konungr segir at honum væri ei sínir menn svá falir at hann vildi vága þeim undir tröllskap hennar. 
Now Sigrgarð asked his father to obtain for himself a force to avenge his dishonour, but (the) king says that his (ie the king’s) men were not so ‘for-sale’ (ie expendible, falr) to him that he wanted to risk them against her witchcraft (‘trollery’)

Kvað hitt ráðligra at vinna með djúpsettum ráðum, “þvíat hon er ósigrandi, ok ætla margir at henni muni ei sjálfrátt um.”
(The king) declared the-other (ie the alternative) more-clever (comparative), to act with deep-laid plans, “because she is invincible, and many think that (it) will not be self-determined (sjálfráðr, Z3) for her concerning (it) (ie it is not within her power, not her fault , ie she is being controlled by external/supernatural forces)

Sigrgarðr hugsar nú sitt ráð.
Sigrgarðr now thinks-upon his plan (course-of-action)

Jónas hét maðr. 
(There) was a man called Jónas.

Hann var ríkastr maðr í öllum austrveg. 
He was the most-powerful man in all (the) East-Way.

Hann átti dýrri gripi enn aðrir menn, ok var hann af því víðfrægr um allan austrveg. 
He had more-expensive treasure than (enn = en, Z3, as Brian indicated previously) other people (men), and he was from this (ie as a result) famous across all (the) East-Way

Hann átti klæði þat at leið í lopti, af náttúrusteinum þeim sem þar váru í fólgnir, ok rúnastöfum þeim sem þar váru í saumaðir, ef þeir væri réttiliga lesnir.
He had that garment that glided (líða, past tense) in air (ie floated, flew), from (ie because of) those stones-possessing special (magical) virtues which were hidden (pp of fela, fólginn, fólgnir, 3 pers pl form) there in, and those runic-characters which were sewn (3 pers pl form of pp) there-in, if they were read (lesa, Z4) correctly.