One option would be to run profiler and log the growth stats for tempdb to a table, you can then correlate any tempdb growth sperts back to a procedure/group of procedures which executed during that time frame.

Personally I would prefer to use Perfmon, and collect the MSSQL$SQL200x:Databases\Log File(s) Used Size (KB) and select tempdb to monitor the growth, rather than running something via SQL Server as the scheduler will only run every minute, whereas with Perfmon you can set the collection frequency in seconds.

The error message you are getting when you execute the stored procedure is due to a column length in the temp table being shorter than the string collected by the stored procedure. Increase the column lengths and the problem will be resolved.

Hope this helps.