Surprisingly a full thickness burn requires only the involvement of epidermis (outer layer of skin), dermis and the fatty layer below. Once the whole layer of the dermis (inner layer) is destroyed the ability of the skin to heal itself is destroyed, hence the term 'full thickness'.< all of your burns are full thickness regardless of penetration past that point, you are right in saying his burns aren't as bad, to me those ones look like 2nd degree partial thickness/deep partial thickness (that’s what I should have said in my post above). the blistering indicates that there is living dermal tissue underneath, in your case there was no blistering because all the tissue had been burnt though.
