I'm not experienced in physics yet (if it helps I've covered as much as acceleration, momentum and energy transfer/chemistry ionic and covalent bonding) but I've heard that the way people compare destructive force of nuclear weapons by megatonnes or kilotonnes is wrong. This does seem to make some sense because the energy will turn into a mix of gamma (?) radiation, light radiation, heat radiation and other things, but is there an accurate way to compare nuclear weapon destructive force? Say, I wanted to compare today's weapons to Little Boy.
The so-called TNT equivalent of a nuclear weapon is an unambiguous way of quantifying how much energy is released by the nuclear weapon. There's nothing 'wrong' about it.
The only caveat is that the damage caused by, say, Little Boy versus 15 kilotons of TNT would not be identical despite having an equivalent yield (for various practical reasons).
Generally, 10-20% of nuclear yield is emitted in the form of ionizing or residual radiation, unlike conventional weapons. Related: effects of nuclear explosions.
Since no nuclear bomb has been used since since Nagasaki we can and indeed do only infer "applications" if you are talking about dropping a nuclear weapon on a human population. These estimates based upon the criteria you have given appear very effective as no theronuclear weapon has been detonated on a population center since Nagasaki, Japan in 1945.
I would read up on Edward Teller and his work on the Hydrogen Bomb and its controversies which were legion since a hydrogen bomb is an order of magnitude more destructive than the two atomic bombs dropped in World War 2 on Japan.