MSHOST should not be 'my_url' it should be the dns name or virtual name, servername or SAP*** (* = SID)
As for the SRCSRV port are you using the port defined in your icm/server_port_XX?
wdisp/system_0 = SID=, MSHOST=(my_url), MSSPORT=xxxx, and SRCSRV=*:xxxx
I'm also not sure where the Cisco ACE comes into play, are you trying to get the web dispatcher to work first and then bringing in the ACE or is it already behind the ACE and its handing traffic off to the web dispatcher?