1-how many addresses are there with this characteristic?
Hard to say. Less than 49
33 (6.0x10
55) because some those would have an invalid checksum.
1- what are the probabilities of finding this type of address?
In a random address, for each digit, the probability of being a letter is 49/58, so the probability of 33 of them all being a letter is (49/58)
33, or about 1 out of 261. It is not that rare.
2- If a brute force code is executed with my code, how many addresses will I find with these characteristics?
If you generate addresses at random, 1 out of 261 will be all letters.
3- as these types of addresses are considerably strange and proportionally in less quantity, does my code make them vulnerable?
Does the owner of "1LdRcdxfbSnmCYYNdeYpUnztiYzVfBEQeC" have a strangely vulnerable address? If so, and read this, I hope you move your
money to a more secure address.
No, because there is no way to generate only addresses with only letters.