For IQFeed contracts which contains '@' sign just use square brackets as we discussed.
For IB futures use this syntax: <Symbol>:FUT@<Exchange>, for example: VUK8:FUT@CFE or HOK8:FUT@NYMEX. It works even for cryptocurrencies - both XBTJ8:FUT@CFECRYPTO & BTCM8:FUT@CMECRYPTO works fine. I spend lot of time on solving CBOT issue and now I have a solution: symbol should be in format <Root><Space><Space><Space><3-letters month code><Space><2-digit year>:FUT@ECBOT, for example 'ZW JUL 18:FUT@ECBOT' works for me.
Forex contracts on IB should use syntax <Currency1><Currency2>:CASH (w/o exchange) - for example AUDCAD:CASH.