Regex

import re

with open("textos.txt") as source:
    fullText = source.read()

    match = re.findall("(\\.\d+.+?)(?=(\\.\d+|\Z))", fullText, re.DOTALL)
    for text in match:
        lines = text[0].split("\n")
        title = lines[0]
        content = "\n".join(lines[1:])
        with open(title + ".txt", "w") as output:
            output.write(title + "\n" + content)