Advise On SQL Server Data Replication
Almost all of your requirements can be provided by merge-replication. There is some information about it in my StairWay series here: http://www.sqlservercentral.com/stairway/72401/

Those articles don't cover replication using port 80 but that is possible.

However, the topology is always a tree. You have one root and the data is distributed through there. A real "distributed agents" topology, where each note can synch with each other node is not possible with the build in tools.