According to Wikipedia an average lightning strike has $1$ TW power, the whole world used $16$ TW of power in 2006.
The lightning strike lasts for $30$ microseconds. Does this mean that you get $100$ TW of energy in just $30$ microseconds?
[Physics] How much energy is in a lightning strike
electricityenergylightning
Related Solutions
The majority of the energy is dissipated in the travel through the air from the cloud to the ground. The energy goes into heating the air and generating the shockwave that we hear as thunder. I can't give you a single definitive refernce for this, but Googling "energy dissipation lightning" will find lots of relevant articles.
You can understand why this is because the energy dissipated by a current $I$ travelling through a resistance $R$ is given by $W = I^2R$. In a lightning strike the current is constant, because the charge flowing in one end has to flow out the other end, so the power dissipated is proportional to the resistance. The resistance of air is a lot higher than the resistance of the ground/tree/person or whatever the lightning hits, so the majority of the energy dissipation is in the air.
The electrons flowing from the cloud through the lightning bolt end up in the ground, but with an energy only slightly greater than ambient. They will presumably flow into the surrounding area until the potential difference around the point of strike falls to effectively zero. This is likely to be within a few metres, so they wouldn't get anywhere near the Earth's core.
A Faraday cage is made to form an alternate path for electricity to travel from source to ground without travelling through the object inside the cage.
So if the Cage is complete then there is no problem in touching the inner surface. That is why people wear cloths out of metallic mesh which also acts as a Faraday cage (check for EMF shield clothing). But remember the cage should be complete, which means the circuit of the cage should be complete.
Best Answer
You are confused about units. Watt is a unit of power (energy/time), Watt-hour is a unit of energy. 16TW is an estimate of the continuous average power usage of the world - which is about 140,000 TWh each year. If the lightning has a peak power of 1TW for 30 microseconds, this corresponds to an energy content of about 8000 Watt-hours.