It seems like the bc1 address is indeed you change address then, but your wallet has automatically sent the change from your legacy outputs to a segwit address. I wasn't aware that Bitcoin Wallet for Android did this.

You can use this 747 satoshi to perform a CPFP transaction, but the problem you have now is that it is not enough to perform a CPFP transaction by itself. You would need to deposit additional funds to your wallet, and then spend those additional funds along with the 747 satoshi in a further transaction. While possible, this becomes significantly more costly since you have to make two further transactions and your second transaction needs to include two inputs.