I'm glad it helped you. When I first learned this saying, it felt "backwards" to me, so I just decided to memorize it and not worry about why. Later, when my Spanish was a bit better I was able to analyze it and see that it really does make sense the way it is.

A ruler is also a straight edge, yet not necessarily a despot.
 

My answer to "No hay mal que por bien no venga." does indeed translate in non literal fashion, as you have deduced!
However, if as you have suggested it should be written ("No hay bien que por mal no venga." It would then mean in the literal : No good ever comes from that which is bad. The original idiom literally would translate to "there exists nothing bad via which from good, it is ushered. This convoluted logic is more than idiomatic, and what is truly meant is numerous #1-spiritual (all good co-exists with that which is not good, necessarily the bad), #2-Philosophical (even the existentially aware is not cognizant of what is good or bad according to when, where, why, what, etc., and so on and so forth.) #3-Morality (What is good for the goose is good(not), but really so for the gander). Just three disciplines for which its usage can apply.

Finally, and as I understand the culture in which it supports [meaning is: all perceived bad is not so, that through it came the good.] All is not truly apparent unless it is examined without biased senses supported by a false belief system. It is part and parcel of the mysterious ways of our creator. Keep in mind that even though all societies have some form of religion of which all of them hold this to be so, however in all Spanish speaking countries, and others (romance languages) e.g.-Italian, French, Portuguese, and Romanian, a more homogenous and highest in percentages practice of Catholicism, and varied are the reasons why, for this tenet of the mysterious nature of God been ingrained by a church that in its infancy had always its "roots" cross planted with those of the state. The wrath of the autocrats, the monarchy, and of the church had shared interest which by themselves would not be allowed to stand. Let not the commoner declare of which he feared the most, lest he be executed for "treason" or be made to sit on a Roman chair for "heresy".

That, mon amie, is my long winded and parenthetically digressed explanation to a rather simple question. By and large, we are not empirical beings, but as Oscar Wilde was fond of stating........you fill in the rest.