Update pagination after hook_apachesolr_process_results()
Instead of using hook_apachesolr_process_results() I figured it was better to use hook_apachesolr_update_index instead.

Following the guidance here: http://www.phase2technology.com/blog/filtering-apache-solr-search-results-based-on-dynamic-fields/

I am now able to create a filter using hook_apachesolr_modify_query that will return the correct results and pagination.