Calculating Expected Value from CDF

I have two questions if someone can help me and give me reference used.

Can we calculate Expected Value (EV) by reading random variables from Cumulative Distribution Function (CDF)? For example, P90 = 467, P50 = 740 and P10 = 1,139? Can the EV be 90%*467 + 50% * 740 and 10% * 1,139.

Can the sum of probabilities be more than 100% when calculating EV? I see the following calculations.

EV = 97% * 467 + 70% *273 + 30% * 399 = 764

The author claims that 764 will be close to P50 = 740 if the data is represented by normal probability distribution.

Another generic connection between the cdf $$F$$ and the mean $$\mathbb E[X]$$ is given by the identity $$\mathbb E[X]= \int^{-\infty}_0 F(x)\,\text dx+\int^{\infty}_0 (1-F)(x)\,\text dx$$ which appears in many X Validated entries, e.g.