Can you please clarify there is the benefit in your method? You are saying that "Now we only have to check the x values from space 0 to 2^(bit-2)", so we need to check 2^(bit-2) combinations. It is just 2 times less that the brutforce of the full range. Not effective.
However in Pollard method we should make only sqr (2^(bit-1)) operations, which is much much less than in your method.
Example: for 110 bit key, you suggest to check 2^108 combinations, but in Pollard method we need only 2^54.5 operations.
So why is your method valuable? What is the main idea and advantage?
The idea is of course to only make sqr(2^(bit-2)) operations.
for #50:
python pollard-kangaroo-multi.py 50 03f46f41027bbf44fafd6b059091b900dad41e6845b2241dc3254c7cdd3c5a16c6
should be equivalent to
python pollard-kangaroo-multi.py 8:FFFFFFFFFFFF 02bc9d041a4839d3bef61e319cd02d3b177292ccb79ed27c1bf6043ab0ec635bfd
(8 is by default minimum bit using pollard-kangaroo-multi.py)
edit: sorry was the wrong pubkey for #50 in first place