If I may, I think most of what you asked relates ONLY to the material world, the one we see when we are here, however that only answers a very tiny part of this existence and the reasons behind it. Most of the things you listed take place because of the law the OP mentioned at the start, namely: free will.

Understand that most of what we see, feel, experience is an illusion, most of the suffering we see around us is part of this experience and billions of souls incarnate on this Earth to have that experience, good or bad. OP or anyone else has no right to stop suffering from happening since each individual incarnated on this planet has consented and chose said experience.

If you accept the concept of reincarnation and you have had say over 500 lives on this Earth across different times in history, do you think it will matter so much who you were or what you did? Rather the focus will be what you took out from that life and experience. Therefore, it will not matter as much if you suffered or had an easy life, what mattered was the reason you had that experience and how that contributed to the overall progress of your spiritual development.

God will never stop life from expressing itself and has absolutely no judgement on one path over another, all are equally valid and ALLOWED to happen. If you want a good life, do and act in a good manner, if you want a difficult life do and act in a bad manner. But bear in mind past actions will catch up with you in this life or the next in some form via karma.

As pointed before, don't take life too seriously because then the illusion takes over and you forget why you are here, welcome any experience, good and bad, accept it and do your best.

There is an interesting story about a rich person that had everything he ever wanted, but then he became jealous of a poor person he invited in his house to eat as he was starving. Why? Because that poor person was so happy to finally have a proper meal and enjoy good food, happiness the rich person never experienced in his richness which prevented that, since if you can have anything, then you lose interest in most things.

I think if you start from the premise that this world, as it is and as we experience it, is just as it SHOULD be and then try to see WHY it is how it is, rather than trying to CHANGE it, we may come closer to understanding it better and how it functions, thereby being able to really change it as we see fit. But at that point you will quickly realise, you can only change YOUR OWN life rather than the life of others. Who are you to decide or change the world when the world may want to experience suffering and pain? You have no right to do that and if you do attempt to change the life of others against their will or consent, you will quickly see how you will be penalised in your own life by misfortune or other events as a result of your actions.

It is a very tricky situation, almost a paradox, that if you walk down the street and someone is suffering, should you help him or not, especially if he does not ask for help. If he does, then yes, if not, what do you do, keep walking?

God exists and sees it all, through your own eyes. He is everywhere. Once you realise we are all part of the same being, then you will have an easier time understanding this world or any world.