Þú spyrr af miklum fróðleik.
You ask good questions.

> 1 en hann lausafé meira:
> What confuses me here is that there is no verb. Maybe this happens in
> Old Norse, though: but he (had) more moveable property?

The verb is not repeated - but its sense is.
You also note that Norse has no special 4th person pronoun;
"hann ... en hann".

> 2 hafði lítinn kaupeyri:
> wouldn't this noun usually be in the plural?
> Any significance to be attached to the fact that it isn't?

It is normal in this context to use the singular;
*kaupaurar would be weird. Compare this to the English
practice of referring to this sort of thing in the singular
(money, wealth). Note also that 'fé' is always in singular
'mikit fé' = "great wealth". ... Then again we have 'landaurar'
rather than *landeyrir.

> 3 fjölmenni - in Modern Icelandic a large crowd, I believe; can it just
> mean "large number of men" in Old Norse, i.e. not necessarily in the
> same place at the same time?

Not to my knowledge.

> 4 ráða fyrir + acc. = to rule over? Could this have connotations of
> "making decisions for"? What is the Modern Icelandic equivalent,
> please?

We still use this phrase (I think).

As for the meanings of ´ráða' (English cognate 'read')
they are so many and so diverse that I have no idea which
came first and which later or how this particular phrase
developed.

> 5 Haleyri - what is the meaning/origin of the name, please?
> Where is it exactly? Does it have a modern name?

The old nominative should be Haleyrr. I think this is
somewhere in Skánn (Skåne). Can somebody help me out?

Kveðja,
Haukur