I will go ahead and respond since you addressed me directly here.
With (a), the designer is culpable for flaws in the design if the designer is both aware the flaws are there and has the capability to remove them (but doesn't). So yes, God causes suffering by choosing to create the conditions for it -- under the premises that God is omnipotent and omniscient, anyway.
With (b), this is addressed in the OP.
With (a), God is incapable of being culpable of
anything at all because God is infallible thus God cannot make any mistakes or be wrong.
Infallibility refers to an inability to be wrong. It can be applied within a specific domain, or it can be used as a more general adjective. The term has significance in both
epistemology and
theology, and its meaning and significance in both fields is the subject of continued debate.
Infallibility - Wikipedia
With (b) The EXISTENCE of Suffering and God's Benevolence are only contradictory by YOUR standard but you do not determine standards for anyone except yourself.
You deliberately ignore the following:
(a) Suffering is often beneficial to humans, and
(b) God is infallible so God can never be wrong or make any mistakes, and
(c) God has more attributes than omnipotence and omniscience.
Ignoring the fact that suffering can be beneficial to humans is ignoring what is unfavorable to your point of view so it is
special pleading.
special pleading
argument in which the speaker deliberately ignores aspects that are unfavorable to their point of view.
https://www.google.com/search?q=special+pleading
You want God to be only two things,
omnipotent and omniscient, because you "believe" those attributes support your argument. But where do you get those attributes? You get them from the Bible. You
cherry-pick the attributes that you believe are useful to you and ignore all the other attributes of God.
According to the Bible God is:
Eternal, Holy, Unchanging, Impassable, Infinite, Omnipresent, All-Powerful, All-Knowing, All-Wise, Infallible, Self-Existent, Self-Sufficient, Sovereign, Immaterial,
Good, Loving, Gracious, Merciful, Just, Righteous, Forgiving, and Patient.
Cherry Picking
(also known as: ignoring inconvenient data, suppressed evidence, fallacy of incomplete evidence, argument by selective observation, argument by half-truth, card stacking, fallacy of exclusion, ignoring the counter evidence, one-sided assessment, slanting, one-sidedness)
Description: When only select evidence is presented in order to persuade the audience to accept a position, and evidence that would go against the position is withheld. The stronger the withheld evidence, the more fallacious the argument.
Cherry Picking