I get the feeling that we are debating at cross-purposes--that we
do not see the same fundamental assumptions, and this perhaps makes
my answers orthogonal to your questions.  I will try again.

Perhaps you believe that nothing exists aside from objectively
observable and provable things.  In that case, I cannot show you
that there is such thing as a spirit or a spiritual need--these 
things do not exist in the realm of the objective, but in the
realm of the subjective.

(By a.a., I assume you mean Alcoholics Anonymous, and not alt.atheism ;)
I would not say that AA "handles" spiritual needs.  Rather I would say
that AA (and other 12-step programs) help people come to terms with their
needs--ie that AA is facilitating the recovery, and that as part of the
recovery, they recognize their spiritual needs, and begin to rely on a "higher
power" (12-step's term) to fill them instead of whatever substance abuse
they had been accustomed to.  (Sorry, there is no objective proof here
either--no way to take 2 identical alcoholics and try to have one recover
by fulfilling spiritual needs, and one without and externally compare the
difference--we are talking about the virtually infinite complexity of
*people* here.)

Spiritual needs could be defined as things that people need in addition to
physical requirements like air, food, sleep, etc.  These are things like
the need for love and acceptance, and the need for meaning in life.  If 
one denies the existence of spiritual things, one would presumably call 
these "emotional needs". The reason Christians call them spiritual needs 
is that they have aspects that are not fulfillable except by spiritual 
means--ie a person could be loved and accepted by many people, and do 
many meaningful things, but still have a need for love, which can only be
satisfied by the love of God.  Now the problem is that there are people who
accept the existence of these needs, and people who reject them.  Since I
believe in absolute truth, some of these people are right, and the others
are wrong.  So here are the 2 possibilities:

1) If Christians are right, then we all have spiritual needs--ie
we all need God.  Those who do not realize that they need God are 
deluded--they just haven't recognized it yet.

2) If Christians are wrong, spiritual needs are an artefact of our brain
chemicals.  Well-adjusted and properly-integrated personalities do not
have such things.  Christians are simply using the concept of God and 
spiritual needs to mask their own inadequacies.

I hate to belabour the point, but the existence of spirits and spiritual
needs cannot be objectively demonstrated or proven, just like the existence
of God cannot.  And yes, this means that there is a risk that all my subjective
evidence is manufactured by my brain chemicals.  But on the other hand, I 
could venture into solipsism and say that there is a risk that everything that
I appear to objectively know is really manufactured by my brain chemicals.

I suspect this is an unsatisfactory answer to a request for evidence and
demonstration of the existence of spirits and spiritual needs, but my assertion
is that such things are not objectively demonstrable.  As I have said before, 
I myself am on the Christian side of agnosticism, having been pushed off the 
fence by subjective evidence.  (And no, I was not raised a Christian, so it 
is not a case of simply accepting what I was indoctrinated with.)