2. No. If the protection does not specify it is from abilities, it is from cards, which includes numbers.
In the case of a non-Warrior Hero, you would be correct.
However, the Hero in the example is Warrior Class, and so PoP is not protected from it.
To clarify, Prince of Persia is protected from the numbers on Silver Enhancements, if the Warrior Class silver character has lower Strength than Prince of Persia has Toughness, then no amount of Enhancement numbers will change that, but if the Warrior Class character has higher Strength than Prince of Persia's toughness, then it can win by numbers.
Just for completeness sake, if you use a special ability to increase a Warrior Class Silver Character's numbers, it will work against Prince of Persia, because the Warrior Class Character actually gained numbers.