Bench mates are those who sit alongside you at the long table (basically a massive plank from a big tree). So those warriors or important people who shared the King's hall and not the general hoi poloi.
In the latter poem above:
The torch is known to every living man by its pale, bright flame;
it always burns where princes sit within.
The torch is a deliberate fire, formed and lit by men, specifically for lighting rather than heat, it represents seeing in the dark, so only those with wealth (knowledge, education, wisdom, status, money etc) have such light or access to it.
From the earlier poem you quote:
"If i see in flames, the hall o'er my comrades heads;
It burns not so wide, that i will not quench it,
I know that song to sing.
and the Olive Bray translation:
A seventh I know: if I see a hall
high o'er the bench-mates blazing,
flame it ne'er so fiercely I still can save it, --
I know how to sing that song.
This seems to be talking about camaraderie, the flames of passion and anger, warriors contesting one another and finding their ranking in the company. A true man will not fear the wrath of his kinsmen nor back away from the fight but they must be able to prove their worth, the tales of honour and warriors deeds are sung in the hall at a banquet. A true warrior has earned his own song.
Therefore the verse is, to my understanding, talking about being amongst equals, having earned your place in the company of warriors and achievers (the torches or torch bearers of their clan).
