stored procedure with multiple statements does not execute all statements when run from job
The answer, it turned out, is something no one in forum land would have been able to guess at, no matter how good with SQL Server they were. It was application-level security that no one here was aware of. 

The CRM database which was the source of the data for insert, contains a table of system users managed on the front end of the application. The vendor who developed the software set it up, but as they left no documentation, no one here was aware of the security layer on the back-end. It was confusing, largely, because the security only affects certain views - so all those other jobs that were working were calling for information from tables and views that were not influenced by the security. 

When testing logged in as me, the procedure worked because I am set up in the CRM table as an administrator, but the credentials used to run SQL Server agent don't even exist in the CRM user table. 

Had nothing to do with SQL Server security, but everything to do with permissions (didn't see that coming)...