It is fine to define God as goodness itself, but like PeterPlato, unless you can subsequently reason about what rules God’s goodness has, you are essentially declaring yourself ignorant of what goodness is.
To make a statement that evil does not equate to suffering is not the same as “declaring yourself ignorant of what goodness is.” In fact, there is a very solid understanding within classical theology / classic theism that equates goodness with being. Being and goodness are essentially transferable. Things are good to the extent that they exist and evil to the extent that being is deprived or removed from that which does exist.
Pain and suffering, are indicators of deprivation, injury or harm inflicted on beings which exist. Pain is sensory awareness of physical injury or harm; suffering or anguish is awareness of mental or personal harm or injury.
Evil, then, is a deprivation or removal of some aspect of being from that which rightly ought to have it. We physically harm or injure someone when by our actions we make them less than they would have been otherwise. That is what doing “evil” to them essentially means. They may suffer, experience pain or anguish as a result, but the evil is not in the suffering, but, rather, in the deprivation. We have ontologically reduced them in some way - physically, psychologically or spiritually
Here is the “sticky” point: If God is Being Itself, the Creator of all that exists, then bringing things into existence or taking them out of existence is fully within his control. He and he alone would have the moral prerogative to decide what rightfully ought to exist or not exist. That determination cannot be questioned simply because there is no being outside of God who could possibly be in a better position to make a more competent determination. That would be the privilege of omnipotence, omniscience and omnibenevolence.
Pain and suffering would then be the normal (God ordained) mechanisms by which we, as moral agents, are aware that we are undergoing some ontological change for the worse. If the change is physical, we feel pain; if psychological or spiritual, we suffer.
If pain or suffering are mechanisms by which harm is signaled, then merely causing someone to suffer pain or anguish, in and of themselves, is not necessarily evil unless the indicators were accompanied by actual ontological privation (harm.)
However, if God has the power to create “from nothing” he, likewise, has the power to restore or ameliorate all that was taken, immediately and without restriction.
We may not like or appreciate the fact that suffering and pain are an aspect of human life, but God is not guilty of perpetrating evil merely because he allows us to suffer. It would be evil of God to unjustly take away what we justly merited to have, but then it would need to be argued that what we did possess (contingent on God’s goodness to begin with) was taken from us and that removal was done so unjustly, in order that such deprivation could rightfully be called “evil.”
It might be wrong for one human being to cause another to suffer unjustly, but that is because the suffering we inflict is typically a signal that unwarranted harm is being perpetrated by the infliction of suffering. It is the harm, however, and not the suffering, per se, that is the evil.
This is clear from the cases where pain or suffering may be present but due to an attempt to bring about some good - vaccinating a child, for example. It is not evil to inflict pain or suffering on a child or patient if these are byproducts of good being done to them or where no good is being deprived (except to spare them greater loss.)