Hello,
1.Based on the
BOL: If you wish to use filters to sync a subset of rows in a column use the Silverlight UI at <LINK>.
It seems that we can apply filters at row level by edit the dataset in the old version of Windows Azure Manager Portal. You can refer to
this blog for reference.
However, in the new version of Silverlight UI, I did not find the link to specify row filter. We can only specify table and column filter in Sync Rules.
2. You can try to register the database with the same agent.
3. I don't think it is support. You can try to add the difference databases in the same Sync Group. But the max number of on premise SQL Server database in a single sync group is five.
Regards,
Fanny Liu