The only way to get a key down from 2^255 to 2^100 is to divide by 2^155.  Meaning you would take that pubkey and divide it by 0, 1, 2, 3, 4, 5, ... all the way to 2^155 (which is a HUGE number) even if your computer could divide and write to file a trillion pubkeys a second, and start a new file once the current file got up to say 1 GB, there is still no way to capture from 0 to 2^155 pubkeys. It would take an eternity. But let us say you did manage to capture those 2^155 pubkeys...now you would have to search each and every pubkey in the 2^100 range to find the one that will give you the private key of the original 2^255 pubkey that you were searching for.

If you would have done like I asked and gave me a random pub key in a smaller range, like 2^40 range, I could show you with examples. 2^255 is to big man, for explanation purposes.