To your first question, yes. You can use the acf/load_field_group hook. This is an undocumented hook and you’ll need to look into the code in ACF. You can use this filter hook to manipulate the fields in the group.
As for the second, you are not creating a single field, you are creating multiple nested fields. It would probably be possible to cram all of it into a single field type by creating a custom field type.
