> enda skal eg hefna hans láta
> indeed I shall avenge his death

I'm not sure about this, but I wonder if 'láta' is the verb: "I shall
have him avenged." i.e. 'ég skal láta hefna hans'. Otherwise,
wouldn't the noun 'lát' "death" be singular here? 'hefna' takes
genitive for the person to be avenged. Compare:

að þú mundir vilja láta hefna hirðmanns þíns
"that you will want to have your courtier killed"

Vildir þú láta hefna þeirra?
"Do you want to have them avenged?"

Hún mun vilja hefna láta Bolla bónda síns.
"She will want to have her husband Bolli avenged."

On the other hand, this interpretation of 'enda skal eg hefna hans
láta' seems to contradict Faarlund's statement in Old Norse Syntax, p.
163 [ http://tech.groups.yahoo.com/group/norse_course/message/6750 ].

"When there are two non-finite verbs in the sentence the normal order
is auxiliary verb-main verb in accordance with the VO (Verb Object)
pattern (1); it is not uncommon however for the non-finite auxiliary
to follow the main verb (2). [...] If the main verb in such a
construction has a complement, this complement may precede its head,
yielding a consistent OV word order (3). [...] The complement may
also follow its auxiliary (4), but it never follows the main verb
directly (5). [...] The reason this is disallowed may be that the
main verb plus the auxiliary was reanalysed as one verbal head after
the OV (Object Verb) order was no longer productive. The
main-auxiliary collocation consequently behaves as one syntactic word,
which allows nothing to intervene." (Faarlund: The Syntax of Old
Norse, 162-163, 8.4.6 "Head-complement order").

1. mun eigi vilja af þér taka
2. því er þú vilt spurt hafa
3. þú vilt honum þjónat hafa
4. hann mun ráða vilja ferðum sínum
5. * hann mun ráða ferðum sínum vilja

So if 'láta' was a verb, our example, 'enda skal ek hefna hans láta',
looks rather close to (5), which Faarlund says doesn't occur.

> Þar var vanur að ganga hafur um túnið
> There a goat was accustomed to walk about the home-field

Yes, I think that's right: "there a goat was accustomed to walk" = "a
goat was accustomed to walk there" -- with "there" having its full
force referring to the location, rather than "there was a goat..."
There's something in the Old Norse Online Course about this, about
'þar' always having that full local sense in Old Norse, never the
reduced 'expletive' sense that 'there' can sometimes have in English,
as in "there was once a king."