Neutron radiation doesn't get contained, and leaves the reactor easily carrying heat with it. That heat has to go somewhere, and so that's what we take energy from.

You can extract heat, in fact you'd have to extract it or let it leak out somewhere. The whole point of it is that it generates more energy than you put in, so energy has to come out somewhere for it to maintain stability.

Gp is just saying that if you cracked it open like an egg (or just had a minor leak even) all that would happen is it would stop fusing. The room this happened in would be a bad place to be, but it's just going to start a fire or something, not destroy the world.