> 1. Are all R's rolled? For example, are both R's in "ormr" rolled? Or both in "dvergr"?
> Sometimes I find myself voicing the first R in these cases as you would an English R, and rolling only the second R.
>
> ( -r represents the R that is being rolled)
>
> orm-r
> dverg-r
> varg-r
>
> What is the correct form?

In the modern language the first r's in the words above are certainly rolled.
I'd worry more about the second r - it may tend to become a mere flap.

I'm not sure what you mean by voice. In the modern language the first r's are
definitely voiced whereas the ending-r may tend to become unvoiced (it's "half-voiced").
In a word like 'virki' (works) or 'skerpa' (sharpen) the first r is fully unvoiced

> 2. Ending R's - do they have tone, or simple an unvoiced flap of the tongue?

Tone? I'm not sure I follow.

- - -

Exactly how r was pronounced in various positions in the Old Norse dialects
is anyone's guess. We know that the r of the grammatical endings developed
out of another sound so I suppose it's conceivable that it was pronounced
as a somewhat different allophone.

Kveðja,
Haukur