Got posted unfinished:
>Dial("SIP/casa1-7552", "IAX2/fwd-gw/*18005551212|60|rwt")
Take a *close* look at that line and compare it to the one on the FWD page:
Dial(IAX2/${FWDNUMBER}:
${FWDPASSWORD}@
iax2.fwdnet.net/${EXTEN:3},60,r)
or to simplify
Dial(IAX2/${FWDUSERID}@IAXpeerFWD/*18005551212,45)