1. Anyone can use the exercises we teach. The primary precaution is: with every practice, pray to your Innermost that through the practice or magical work, only the will of God be done, not your own.
2. Elementals are only a threat when they are being directed against us by ignorant or foolish people. There are many ways to defend oneself, such as with Conjurations, the magical circle, etc. Willpower would only be sufficient if the elemental is a weakling, or you are a Master. (Neither are likely, so it is best to use prayers and conjurations)
3. A tool is only used when it is needed. The same is true of spiritual tools. Use them when you need them. In daily practice, we need meditation in order to analyze our defects, learn about virtues, and awaken consciousness.
I recommend against blending or modifying practices. We are asleep, spiritually blind, in ignorance. A blind man cannot lead himself on a dangerous path. We need to follow the guidance of those who are awake. Therefore, I recommend that we use the practices that we are given, without changing them.
It would be very sad if we wasted years of efforts simply because we foolishly thought we could successfully modify the techniques we were given.
As to the techniques you know, I cannot comment on them. Even within the Gnostic tradition, there are many who are taught meditation, but do not practice correctly because they were taught badly, or did not listen to the instruction, or think they know better than the instructor, or the instructor was wrong in their own interpretation, etc, etc. Just quoting the name of a technique does not imply that it is effective, accurate, etc.
The only way to evaluate a practice is if it is awakening your consciousness.