> "Vilt þú gefa mér þá," segir Gunnar, "og hætta til hverju eg launa þér?"
> "Do you wish to give them to me," says Gunnar, " and risk until when

I reward you?"

I think, here 'þá' = "then" (in the sense of "so, in that case..."):
"Will you give me [hay and food] then?" The two items are neuter
(hey) and masculine (matr) respectively, so presumably they would
collectively need a plural pronoun, rather than masculine: compare
'bæði mat og hey' later on in this section. And note that neuter
singular has just been used as a default for each (hvárttveggja,
hvártgi). I imagine Gunnar has in mind the formulaic conversation
that crops up a few times in sagas, where someone refuses to sell
something, then gives it, e.g. from Ögmundar þáttr dytts:

"...Viltu selja mér feldinn?" (Will you / do you wish sell me the cloak)

Ögmundur svarar: "Eigi vil eg selja þér feldinn. En ef þér líst vel á
hann þá vil eg gefa þér." (I will not sell you the cloak. But if you
like it, then I'll give you it.)

'hætta til' "to risk" + dative object 'hverju eg launa þér' "whatever
I [may decide to] repay you."

> Aldauða

"Completely dead". MM & HP "dead and buried".

> ræna þá

"Rob them" rather than "steal them". With 'ræna', the victim is
accusative, while the thing stolen (what they are robbed of) is dative.

> "Með engi rán munum vér fara," segir Gunnar.
> "With no plunder will we go," says Gunnar.

In other words, we won't be going committing any robbery.

> "Það spara eg eigi," segir Gunnar.

"I will not hold back (withhold, shrink) from [doing] that," says G.

> Er þar öðrum eigi góðs von er slíkir fá eigi.

"There is not a hope of good there for others when such men [as
Gunnar] do not get [good there]." (That's to say: if such fine men as
G. don't get anything, what hope is there for the rest of us.)

MM & HP: "There is little hope for others there when men like Gunnar
cannot buy."

von = ván (noun), feminine nominative singular: "hope, expectation".
Genitive is used for the thing which is hoped for.

slíkir, masculine nominative plural.

> Er þér miklu drengilegra að fá honum bæði mat og hey er þig skortir

hvortgi til."

miklu, neuter dative of 'mikill' (neuter used adverbially).
drengilegra, comparative (neuter).

"It is (i.e. would be) much more gallant of you to give him both food
and hay when (seeing as) you are short of neither."

> austan af Síðu.

"from the east, from Sida" (rather than "from east of Sida"),
according to MM & HP.

> Nú er þar til að taka
> Now is time to take up

As in "take up the story", "now it's to be told (that Hallgerd...)"

LN