There is no official/documented way to create brainwallets (words to privatekey).
You are talking about "privatekey to WIF" which is something different.

I only wonder if the creator is/was close to Satoshi?
I think the creator is watching these forums. Maybe he likes to give a little background. Would be interesting.

Sure you can: R of the signature is the X coordinate of the curve point nonce*G. So you can use kangaroo to search for (R, y) and (R, -y). Then you would have the nonce k and could solve for privatekey.
And it usually is a sha256 hash for the message but I don't think ECDSA specifies a hashing algorithm so you can use whatever you want for the hash as long as the other side knows what algorithm you have been using if they want to rebuild the hash from the message.
So I think you should refresh your knowledge of ECDSA .

What you are doing is basic math:
5/2 = 2.5
2.5 -2 = 0.5
0.5 * 2 = 1

Now lets do it for 123123:
123123/2 = 61561.5
61561.5 - 2 = 61559.5
61559.5 * 2 = 123119

So we substracted 4 from 123123...

Now bigger divisor:

123123 / 4234  = 29.07959376476145
29.07959376476145 - 4234 = -4204.920406235239
-4204.920406235239 * 4234 = -17803633

Ok. This seems to be some advanced math I do not and will not understand.

It is really hard to follow your text full of errors/typos.
Sure you can divide the public key by any number you want, but what does it help?

You can imagine the simple example of dividing by 2.

What are you trying to do?

You can divide a publickey by 2 but you don't know if the corresponding privatekey is even or odd so it either is 1 bit below or somewhere else...