a. Joe's somewhat a philospher. | This means, "Joe's a philosopher, partially." It's correct, technically, but not a common construction.
a (part II). Joe's somewhat the philosopher. | This means, "Joe belongs partly to the philosopher archetype."
b. Joe's somewhat of a/the philospher.
This is something of an idiomatic phrasing. Cambridge Advanced Learner's Dictionary says,
Used to describe a person or thing in a way that is partly true but
not completely or exactly|
It came as something of a surprise.
He has a reputation as something of a troublemaker.
I have a biology question for you - I gather you're something of an expert.
c. Do you know if Sam's much a poker player? | Nope. You can say "much water" because "water" is a mass noun (as opposed to a countable noun,) but you can't say "much a poker player" because "a poker player" isn't a mass noun.
d. Do you know if Sam's much of a poker player? | Sure. Adding "of" means you're dealing with fractions of player, not a single player, and fractions are continuous (though not in quite the same way decimals are,) not discrete, more like a mass.
e. Do you know if Sam's much the poker player? | Sure. This asks if Sam is or is not a standard poker player. It's like liote in question form.
f. Do you know if Sam's much of the poker player? | Nope. "The poker player" could refer to a specific player, in which case it wouldn't make sense for Sam to be much of him or her. It could also refer to the poker player archetype (not generally an archetype I think of!)
g. There's much the wolf in you. | Nope. I'm rejecting this because, even though you could say there's an implicit "of," it's a little too much processing to add both an "of" and parse "the wolf" as an archetype instead of a literal wolf. It's really a stretch unless you have more context, so I'd say this is shaky at best.
h. There's much of the wolf in you. | Sure. This means you ate your fill of the wolf, or that you strongly exemplify the characteristics associated with the archetypical wolf.
i. I'm not much a writer. | Sure. This is a little strange, but the "of" is implicit.
j. I'm not much of a writer. | Sure. This either means you write only a little, or it's a litote that means you are a bad writer.
k. Much money is on the table. | Sure. This means exactly what it sounds like.
m. Much of the money is on the table. | Sure. This means a large part of, but not all of, the money is there.
n. I spend much time on my homework. | Sure. This means you are studious.
p. I spend much of the time on my homework. | Sure. This is like n, but "much of the time" expresses the time you spend not just as a lump sum, but as a portion of a whole.
q. There is much difference between Syndey and Vancouver. | Probably not. This should be, "There are many differences between Sydney and Vancouver." Using "difference" as a mass noun is a bit of a stretch.
r. There is much of a difference between Syndey and Vancouver. | Nope. This would mean, "There is most of a single difference between Sydney and Vancouver," which is probably not what you mean. If, for some reason, you did mean that, you could make it clear by saying, "There is part of a difference," or, "There is much of a single difference."
s. There's not much difference between Syndey and Vancouver. | Sure. This means there is some difference, but it is not appreciable.
t. There's not much of a difference between Syndey and Vancouver. | Sure. This means there is a small difference, but not a significant difference.