Welcome the Technical Support section. Help us in assisting you by providing us with a concise and descriptive elaboration of your issues. Be specific and if possible, provide us with a step-by-step instruction in replicating your problem.
The migration process will be migrated via current cron job.
"Cron jobs / Scheduled " you just skip this configuration, this is not related with chat migration.
Per cron the message date will be transfered 100 records.... if you need transfer it faster you can modify this file components/com_community/libraries/cron.php find this code
1. Maybe its coming from different message subject on old message, please check again.
2. maybe that mail is coming different message? you can track the mail queue from Jomsocial backend->Monitor->Mail Queue
3. Delete message is under developing now.. we will let you know when its available in next version