I have bitcoin in blockchain.info (where i control the private keys) before 25 Oct.
Which exchange/wallet can i use to split the bitcoin into BTC and BTG so that i can sell them separately before 1 Nov 2017?
There are no such wallets yet that let you split bitcoin gold at the moment except the yobit exchange.
Yobit supports both bitcoin gold and its exchange since the day fork has happened .
It will some time for blockchain to split bitcoin gold from our wallets but if you can't wait anymore, just move your bitcoins to yobit account and there you will be able to see and exchange your bitcoin gold attached to blockchain.