I’ve never really bought into this “powering out of trouble” argument. Once you start accelerating and the other guy does too, whatever trouble you were trying to avoid is suddenly a lot closer and happening at greater speeds. Do that a few times (and I have) and you start to wonder if braking might be the safer option. Regardless, just about every bike is faster than just about any car on the road so using as a justification to buy a more powerful machine does not really hold up for me.
Can’t really help you on the HP/torque thing, but I don’t think it is a simple safe/not safe argument. The more power you have the less room for error you have.
You have probably heard this before but it really is true, your first bike will not be your last (assuming you don’t scare yourself to death!). Why not plan on getting a smaller used bike, even if it’s only for a few months? Take this pressure off yourself, plan on riding a used Ninja 250 for the first 3 months and then get yourself the 600cc knowing you will be able to handle it. You might even turn a profit on the Ninja.