Were you able to resolve your issue?
I find that using PortQryV2 is a bit better than telnet to diagnose issues with SQL Server. See if you can query the necessary ports on your SQL Server instance when connected to the other router
TCP 1433 is the default TCP port for a default instance. if it's a named instance you'll have to look up what it's using.
UDP 1434 is what the SQL Browser uses
There are no special teachers of virtue, because virtue is taught by the whole community.
--Plato