I have read dozens of threads saying you need to keep your BTC on a hardware wallet or paper. Anything online isn't safe they say. When trading that is not really feasible is it? I like to move in and out of positions several times a day and often at a moments notice. My trading account has a sizable balance (to me - 5 figures) in it.
How risky is this and any additional things I could do?
Read all about Mt. Gox and Bitfinex hack and look how many people lost a lot of funds in those trading platform. I'll just advise you to just enough funds in a exchange for your trading purposes and pull out most of your funds to a secure wallet. Its better to be safe that sorry. If you are willing to let all your funds then take the risk, enable 2FA and make a strong password if they planned to hack your account only. But if its a widely planned exchange hack, then nothing you can do. Its up to you dude. I hope you make the right decision.