0 is not defined as 0 * x = 0 - that is a derived formula. 0 is defined as the additive identity, i.e. x + 0 = x = 0 + x. It is a unique number.

0 * x = 0 is proven by noting that 0 * x = (0 + 0) * x = 0 * x + 0 * x (distributive property) and then subtracting the additive inverse of 0 * x from both sides to get that 0 = 0 * x.

However, this says nothing about 0^0, and one cannot talk about 0^(-n) for natural number n since 0 has no multiplicative inverse.

Also your argument on limits is not correct - you chose a particular path of approach for the expression y^x fixed along y = 0. Looking at another angle, the limit of x^x as x approaches 0 is clearly 1 as reasoned in the article, so this causes a clear disagreement here since you can argue for different values to make sense by tweaking the path of approach of the two dimensional function y^x appropriately.