Hello Paul,

> "Ekaayano aya.m, bhikkhave, maggo sattaana.m visuddhiyaa,..."
>
> Is this the "only way" for the purification of beings or the "direct
> way"?

It means "leading to only one place", i.e. Nibbana. For another context
see Mahasihanada sutta (MN I 74):

37. (1) "By encompassing mind with mind I understand a certain person
thus: 'This person so behaves, so conducts himself, has taken such a
path that on the dissolution of the body, after death, he will reappear
in a state of deprivation, in an unhappy destination, in perdition, in
hell.' And then later on, with the divine eye, which is purified and
surpasses the human, I see that on the dissolution of the body, after
death, he has reappeared in a state of deprivation, in an unhappy
destination, in perdition, in hell, and is experiencing extremely
painful, racking, piercing feelings. Suppose there were a charcoal pit
deeper than a man's height full of glowing coals without flame or smoke;
and then a man scorched and exhausted by hot weather, weary, parched and
thirsty, came by a path going in one way only and directed to that same
charcoal pit. Then a man with good sight on seeing him would say: 'This
person so behaves, so conducts himself, has taken such a path, that he
will come to this same charcoal pit'; and then later on he sees that he
has fallen into that charcoal pit and is experiencing extremely painful,
racking, piercing feelings. So too, by encompassing mind with mind...
piercing feelings.

http://www.accesstoinsight.org/canon/sutta/majjhima/mn012.html

With metta, Dmytro