Not sure about the energy point. I assume you mean when attaching to oxygen to make water?

Mass though, it has to do with the amount of neutrones. Helium needs more neutrons to stabilize itself thus adding more weight to it. Normal Helium also can not for bonds meaning it doesn’t react thus can’t produce or take energy because it’s electron ring is full of electrons. No pressure to fill the ring with bonding to another element

Heat denatured their code. Their lipid layer would just disintegrate when dried. If a cell gets damaged then that same stuff can hurt a virus.

Now for how they act. The virus is in a host and reproduces and then is some way transferred to another host. Like cough/sneeze, or other bodily fluids. They hop around until a new host and that’s how they operate