This tutorial is awesome! long time ago I wanted to understand these small parts of the code! but the code is still complicated for me (a lot of lines to search in).
The only part that I did not understand is this:
used_power = (weighted_voting_power + max_vote_denom - 1) / max_vote_denom

max_vote_denom is always equal to 50... means something like "50 votes are regenerated in 5 days"... because the vote_power_reserve_rate is the number of votes regenerated per day (Source).

Any ideas?
Good work. Thank you.