Yes 2FA enough. The security concept is "what you know and what you have". In other words, you *know* your username and password and you *have* your personal phone (or IB issued security device). Obviously your username/password can be leaked from a security breach or more likely you're reusing passwords from multiple sites or using weak passwords. IB's username policy actually makes this less of a problem since you can't choose your own username. So even if you reused a leaked password an attacker still probably doesn't know your username. Losing your phone is very unlikely since people are very protective of them.
Is it possible to bypass 2FA? Yes, if you've been specifically targeted by hackers and they have the ability to sniff your smartphone data. In other words, it's very hard and very unlikely.
IP restrictions are fine except for when you're traveling and want to trade.