For years, advice on how to solve the following problems

1, from the server Slave_SQL_Running_State: Waiting for Slave Workers to free pending events
2, Seconds_Behind_Master: 67354
3, Relay_Log_Pos: 320, hasn't been changed
4, slave - pending - jobs - size - Max value is less than the main library max_allowed_packet, last night in the circumstance that did not stop slave, slave - pending - jobs - size - Max is greater than the max_allowed_packet (stop slave once before, very slowly, so I hesitate to don't stop)
5, Relay_Log_Pos corresponding to a heap of Delete_rows, corresponding to the innodb, but there is no primary key