WRONG

_balances[msg.sender] = _balances[msg.sender].sub(tokensToTransfer);

CORRECT

_balances[msg.sender] = _balances[msg.sender].sub(value);

What have I done wrong?

WRONG

_balances[msg.sender] = _balances[msg.sender].sub(tokensToTransfer);

CORRECT

_balances[msg.sender] = _balances[msg.sender].sub(value);

Why has nothing been sent to the contract?

I didn't see any code to add balance for contract