What do I do with the list of blocked IP addresses
We've all been there and felt that. 

This is time consuming.  You could report the abuse to the abuse@domain.xyz email by looking up the Whois record for each IP.  This email address and investigation are required by ... 


  The 2013 Registrar Accreditation Agreement (RAA) requires
  ICANN-Accredited registrars to provide abuse contact information and
  take steps to investigate reports of abuse. This includes:
  
  Maintaining an abuse contact to receive abuse reports involving domain
  names sponsored by the registrar, including reports of illegal
  activity, and publishing an email address to receive reports on the
  home page of the registrar's website;
  
  Taking reasonable and prompt steps to investigate and respond
  appropriately to any reports of abuse;
  
  Establishing and maintaining a dedicated abuse point of contact to
  receive reports of illegal activity filed by law enforcement or other
  similar authorities designated by the government of the jurisdiction
  in which the Registrar is established or maintains a physical office.
  The registrar should review such reports within 24 hours of
  submission. This includes a dedicated email address and telephone
  number that is monitored 24 hours a day, seven days a week;
  
  Publishing on the registrar's website a description of its procedures
  for the receipt, handling, and tracking of abuse reports; and
  
  Providing an abuse email address and telephone number in Whois
  results.
  
  The full abuse contact requirements are provided in Section 3.18 the
  2013 RAA.


CleanTalk.org and abuseipdb.com  will accept the IPs and emails you find as spam.  One at a time though so start with the biggest offenders.


  When you sent a report, the IP or Email address with malicious
  activity will be added in our blacklist database with status
  "Suspicious". If we will receive other abuse reports so the status
  will be changed to BlackListed.


Spamcop.net will take spam emails you find then sends "warning information to the internet service provider responsible for hosting the services used by the spammer (web sites and email sending sites)."

Rather than "a growing list of blocked IP addresses", have you considered blocking by country or region or IP range?  You can do that through the .htaccess file or Drupal modules.

I hope this gets you started in your crusade for a better world.