Answers can be found in the Space Wolf
FAQ:
Q. Can an Independent Character who has taken
Fenrisian Wolves as wargear join another unit as if he
were on his own? (p31)
A. Yes – in fact you could potentially have a unit that
included several Independent Characters, all of whom
have Fenrisian Wolves, though each set of Fenrisian
Wolves must still remain within 2" of their Independent
Character master.
Q. Do Fenrisian Wolves bought as wargear by an
Independent Character act as a Retinue during an
assault? (p31)
A. No – the Independent Character may still be singled out
even though his Fenrisian Wolves are still alive. For
example, a unit of Blood Claws is joined by a Wolf Lord
with two Fenrisian Wolves as wargear. In an assault, the
enemy would be able to direct his attacks towards three
separate targets – the Blood Claws, the Wolf Lord, or the
Fenrisian Wolves.
Don't necessarily agree with those, but it's not up to me.
As for your last question, this might help a bit:
Q. The Lone Wolf rule Pack of One states that a Lone
Wolf may never be joined by other models. How then can
a Lone Wolf purchase Fenrisian Wolves as wargear? (p29)
A. The Fenrisian Wolves are counted as wargear and are
therefore an exception to the ʻPack of Oneʼ rule.
It doesn't say that they do not count as models, and makes mention that they are an exception to his rule regarding other models. This means that they do count for models for casualty/morale purposes, and you'd have to take a test.