I'm with Cimics. I'm not sure I can accept the terms of your argument. I was hoping the syllogism would help us. One of the comments I centered on was this one:
"So some kind of substance must be able to exist without creation. For a creator to exist it would have to have arisen from this substance by some unguided process."
I agree with the first sentence, but probably not in the same way you mean it. But not the second sentence.
A syllogism typically has this sort of form:
A. Such and Such
B. This and that
therefore
C. such and such and this and that.
Not really profound really- the conclusion (C) usually is just a simple combination of statements A and B. You can create syllogisms that are valid but not necessarily true:
A. All men have heads.
B. Here is a man.
therefore
C. He has a head.
The syllogism works because we have to assume A and B, but these assumptions might not be true. In this case, in B, 'here is a man' it is logically possible that we've been presented with a de-capitated man, so the conclusion, while valid, may not be true. But all that means really is that our assumption in A is not really narrowly construed enough. I could suggest better formulations of A, but this is a family friendly forum.

However, if we can create reasonable (or even better, unassailable) assumptions, we can use a syllogism as a reliable way to create 'new' knowledge, or at the very least, we can use it to isolate the logical steps in our arguments.
Let's start forming a syllogism for our use.
A. "Something must be able to exist without creation."
I derived that from the statement I quoted above. I largely agree with this. To head off some ambiguities, I like to take the word 'something' and break it up thusly:
"The sum of all that is real" must exist without being created.
Problems inherent in our language typically give ourselves two options to choose from- God, and the universe. Basically we are arguing about the nature of the final regress. However, with crazy-butt theories like the multi-verse running around, we cannot so easily use the word 'Universe' as our strictly materialistic alternative. Furthermore, even though Christian theists mean 'the sum of all that is real' as part of the very definition of God, this fact is often mis-understood or even ignored.
So, to escape all of that, in discussions like the one you and I are embarking on, I substitute for 'something,' 'the sum of all that is real,' and because that is too hard to type all the time, I just put 'x.' That way no one can say we are assuming any of our conclusions.
So- if you're still with me-
'x'='the sum of all that is real'='something' [from your statement and the syllogism letter A above]
So, finally:
A. 'x' must exist without being created.
I agree with this assumption, and believe it can be argued forcefully if driven to defending it. But maybe you already agree with it? If you do, I can try to formulate a 'B.'