p=75223
n=74929
E = EllipticCurve(GF(p), [0, 7])
Your example is much weaker than secp256k1, not only because you use small numbers. It is weaker, because the greatest common divisor of (p-1) and (n-1) is 42, while in secp256k1 it is only 6. Also, because p-value and n-value can be sometimes combined, and because you use b=7, that greatest common divisor, equal to 42=6*7 is a bigger weakness, because not only you can apply the same attacks, as in secp256k1, and calculate famous six points to get private key in 2^128 steps, instead of 2^256. In your example, you can also attack by using 7, and because your curve equation is y^2=x^3+7, then imagine what would happen if you start picking (x,y) pairs, where both numbers are divisible by 7.