Re: backfeeding. Please, pretty please, with a cherry on top, don't. Just don't.
I'm not licensed for current carrying wiring, but I am comfortable with the science, and do have professional experience with data wiring, several types of audio, and some endpoint telecom stuff. The theory crosses over completely, even if the installation codes don't at all.
Given a suitable ground, all you need to carry current is one wire. See earth-return systems. Main breakers do not disconnect the neutral; therefore you have the one wire. Not all installations bond the neutral and ground at the panel and even if it does, residential ground rods often make a lousy connection to the earth. So, don't count on the neutral being electrically clamped to ground. Think of it as essentially hot; it can become actually hot under some non-fault conditions; not full voltage, but enough to bite.
Something often missed about electric circuits is that, in any series circuit, the current is identical throughout the circuit at any given time. Or, in layman's terms, what goes in must come out. If you're drawing 20A at 240V, there's 20A coming through each pole of the breaker. If you're drawing 10A at 120V, there is 10A going through the hot and 10A going through the neutral. It isn't just waste or spill being sent down the neutral; it's not like a pipe delivering electricity to you. It's more like sticking your hand into a river. If it wasn't all flowing past you, there'd be no pressure on your hand.
Consider the circuit again with that in mind.
Generator sends +/- 120 into the panel, some of which goes straight through as 240V, some lesser amount coming back along the neutral as 120V. Neutral is therefore no longer at ground potential, to some greater or lesser degree. However, neutral is touching someone else's loop and able to exchange electrons with it.
Imagine a stream running within inches of the mighty mississip. Now imagine the river drying up, to simulate the power outage. Now knock down the separating wall, and observe insignificant, but nonzero, amounts of the stream leaking out into the riverbed.
Now, restore the river, and stand the hell back. What just happened to your generator and anyone standing near it?
Clearly, this doesn't happen every time someone does this, but it can if conditions line up right.
If you really must use the house wiring to supply your key appliances from a generator, here's my suggestion. It probably isn't code, but I'm perfectly comfortable asserting that it's safer than what you're doing.
Install a small main-lug subpanel next to your existing main breaker panel. Move all those key circuits over to it.
Instead of hard-wiring the subpanel, connect it via a 3-wire-plus-ground plug and receptacle to the main breaker panel. Also connect a hardwired ground between the two. (BUT NOT NEUTRAL!)
Then, when the power goes out, fire up the generator, drag its extension cord down to the basement, and plug the whole subpanel into it.
Then, when the power comes back on, there's absolutely no cross connections and no safety hazard. Stop the generator, plug the subpanel back into its dedicated outlet, and close its feeder breaker in the main panel.
Let's describe this as "specialty manual transfer switch, at the end of your arm." All organic, fully green technology.
Guys, if that idea is in any way actually viable, please modify for code compliance...