1. First, Bardon stresses magnetic bathing / showering of the whole body, not just eye baths. Eye bathing is more of a vision remedy and while it may accelerate development of clairvoyance later on is less integral. Next, feel fre to take an evening magnetic wash / brush if you'd like, but remember not to overstimulate your skin with abrasion or your skin and hair by excessive washing.
Magnetic bathing is useful for clearing off negative energy, especially when combined with a visualization. It's recommended after stressful days or time spent in negative situations or with negative people. However, remember that water's magnetism will also wash away any positive energy which you have accumulated in energy work (which takes a few hours to fully affect your subtle bodies). For this reason, bathe before energy work if possible, and wait a few hours afterwards before bathing. If you must bathe after energy work, use hot water, keep it short, and visualize the energies being retained. At this point in your training, you are not doing energy work without a medium (air, food, drink, etc.) but by Step III when you start with the elements and vital force, this should be remembered.
2. The purer the water the better. If you can get distilled water, that will work. The reason it is boiled is to make it sanitary for your eyes and to temporarily remove the magnetic property of the water to release any impressions that it may have stored. Therefore if you use well-filtered water, it will be physically safe, and the hotter the water has been made previous to the eye bath, the more metaphysically pure it will be.
3. You can, but the IIH is a complete system in and of itself and most purists won't recommend it. Take psi, for instance. You COULD learn psi, or you could look over what you've learned and realize that if you use the visualization of Step II to make a form and then impregnate it with a function as outlined in Step I, you have created a psi construct. If you get to Step V, it's easy to see that telekinesis (in the hermetic paradigm) can be accomplished in a few different ways - the projection of the air element, perhaps, or maybe realizing through the Akasa principle that your consciousness may infiltrate the being of the object and thus influence it. This is analogous to the active psi idea of "kineting with the soul," if a little more segmented. Personally, I think that if you're interested in psi, you should do active psi, and if you want to do the IIH, stick with magic.
4. Earlier / faster does not always mean better. I've got a long explanation for this question.
For projection in general, that's a good book for the prepared individual. I used it when I was starting out (and was not prepared) and got sufficient results to prove that it works. Unfortunately, I've been convinced over the years - partially through my own heart-attack-like experience in which my heart chakra activity failed to produce a projection and put my physical body into a state of shock - that projection isn't as perfectly safe as it's popular to believe that it is nowadays. For one thing, the mental body is more commonly projected, not the astral body, making the "astral" projection most people are familiar with actually mental projection. The astral body of the untrained individual doesn't normally stray more than a few feet from the physical body unless that individual has died or is very near death. The astral body is directly responsible for many physical life processes and therefore if it experiences damage during projection, the individual can come to physical harm. The mental body is safer in this regard, although sustaining damage to the mental body can still cause mental or emotional trauma which can later manifest physically if not corrected.
The reason projection is taught in the IIH at a relatively high Step is because Bardon wishes the student to attain the magical / elemental equilibrium. The equilibrium makes the projector incredibly difficult to harm (or glamor, or coerce, or trick, or trap) on astral and mental levels, and therefore the projector has time to end the projection if they decide the situation has turned sour. Furthermore, at this stage, the individual will be able to differentiate between their astral and mental bodies and project the one which is desired (and safest) each time.
Conversely, Robert Bruce does not adequately train the projector to differentiate between astral and mental bodies and doesn't really address the issue of psychic self defense, except in a completely different book (Practical Psychic Self-Defense), which deals mainly with non-projection defense, and even then discusses primarily countermeasures against existing problems and not techniques which prevent "negs" in the first place, or address the possibility of the individual magician doing something stupid and hurting themselves. He also occasionally recommends things like burning sulfur which, while effective, is potentially fatal if improperly performed and honestly probably shouldn't have been recommended to the public to begin with.
The reasons that Robert Bruce doesn't get much grief for his system (and why projection is widely regarded as safe for the untrained), as far as I can tell, are:
1. Those who give up before they are successful won't complain, obviously.
2. It generally works for people with past-life projection experience and
3. It generally works for people who have already achieved equilibrium through previous spiritual practice but
4. Groups 2 and 3 (Oh, including Robert Bruce, for the record) are naturally protected anyways as I explained before, and therefore may be unaware of danger.
5. Many people project from dreamstate, which naturally uses the safer mental body while the dormant astral body hovers safely near the physical sleeper.
6. Most inexperienced projectors have extremely short projections in which the potential for harm is extremely low.
7. If someone DOES experience psychological trauma during projection, medical specialists chalk the belief in projection in the first place up to pre-existing insanity.
8. If a projector in their astral body were to, say, die, the coroner would be unable to connect the death to a botched projection.
9. People who have projected only a handful of times (including me, when I began) tend to parrot the dogma of their teachers, who tend to be groups 2 and 3. See number 4.
and finally
10. Before something dangerous happens, the projector will usually be in an environment which is scary, because the higher planes tend to reflect essence in form. Therefore, something about to hurt you will manifest violent imagery in the surroundings, often before attack, for example. This will in turn scare the projector which will in turn often shock them safely back into their body. Newsflash: Just because you escape doesn't mean you were safe to begin with. Furthermore, telling everyone that they are safe potentially eliminates this vital fear response, removing the defense mechanism to begin with.
Having been a part of Astral Dynamics (Robert Bruce's site / forum) for long enough to read some of the crazy psychic attack horror stories that I have, it boggles my mind that the community in general is so blithely dismissive of the idea that safety is never a guarantee in metaphysics.
For future reference, the opinion that I am expressing is not a popular one. I am aware of this. I've also been in these communities for several years and have yet to meet people who have been torn up during projection that have convinced me that it was an altogether "safe" experience. Robert Bruce's method will give you results, but if you'd like to try it out I recommend getting to the point in the IIH first. Chances are you'll begin finding yourself out of your body occasionally before you get to that Step anyways.