Some questions about Elves, the Halls of Mandos, and Valinor

[Inziladun]

Welcome, narsil! I'll give it a go.

(1). I know one of the HOME books touches on this, but sadly, I don't have them. Basically, I don't think there is any set time limit an Elf must remain in Mandos before being re-bodied, save that in some cases certain Elves guilty of evil deeds (such as Saeros, who had taunted Túrin and attacked him in Doriath) must wait longer than others.
I know of no Elves other than Glorfindel that are named as being re-bodied in Middle-earth, but that is no indication that others had not done so.

(2). Any Elf arriving in Valinor should be able to physically meet any of their Elder Days kin who weren't confined in Mandos.
As for Fëanor, The Silmarillion indicates that he at least had not be released:

....his likeness has never again appeared in Arda, neither has his spirit left the Halls of Mandos.

Of the Return of the Noldor

The verdict on his sons is not clear. At least one of them, Maglor, might have still been alive in Middle-earth at the time of the war of the Ring. I would think the others would have had a long stint in Mandos, especially Celegorm, Curufin, and Caranthir.

(3). Valinor / Aman is a place where nothing dies. That is contrary to the mortal nature of Men and Dwarves, and, as explained by the Eldar to the Númenóreans, being in such an environment is simply too much for a mortal to long endure.

(4). I've pictured Valinor as being more beautiful than anything in mortal lands. As fair as were Lórien and Gondolin, I think they were only pale copies of the landscapes and cities in Aman. The Simarillion said of Tirion, that as Eärendil walked through it:

....the dust upon his raiment and his shoes was a dust of diamonds, and he shone and glistened as he climbed the long white stairs.

Of the Voyage of Eärendil

When the very dust has beauty, what compares to that?