For your 4th question: Nested MIGXdb
You need 2 configs and the relationships in your schema have to be set correctly.
In your config for Company add a field of “Input TV type” = migxdb and “Configs” = name_of_your_staff_config
In your config for Staff in the tab “MIGXdb-Settings”, set “Join Alias” to the alias of the relationship in your schema and “Check Resource” to yes. Maybe also set “Load Grid” to auto.