Most of them are just overly optimistic. Overestimating the size/power/destructive power of things that ultimately would be little more effective as weapons than firecrackers (though like firecrackers, more than capable of maiming the handler...)

If you wanted to make such a book properly, you would be best off describing things that you did not invent (or worse, dream up but never tried) but instead things that have actually been used. For example, describe how the Finns used storm matches to make Molotov cocktails (which they used to great effect against Soviet tanks, though modern tanks will not be vulnerable to those sort of attacks. That should also be mentioned prominently in this hypothetical "Cookbook-done-right.")

The sabotage idea is the most likely to me, since anyone who would have written the articles probably would have tested the ideas first, and realized how stupid and unworkable they were. Instead it purports to be a real guide, so either it was written by a total moron, or someone who knew the recipes would end up backfiring. The time at which it was written is filled with examples of USG trying to subvert or break up anti-war groups, so it's not unreasonable to assume they might produce misinformation like this.

In order: Usually; almost always, especially when involving fun stuff like nitric acid; that question's answer depends on whom you ask, but I tend to doubt it.