the central thing here is whether God's love - specifically the God of Abraham & Isaac & Moses, manifest in Jesus Christ - can be proven genuine.
everywhere in the Bible when God's actions and/or intentions are questioned - not just Job, or Paul's eloquent argument in Romans 9, or Jonah, but also in the books of the prophets and implied in Ecclesiastes & the proverbs - in every case the answer given is "who is man to question God" -- it's called by men a philosophical "rabbit hole" to assert God's sovereignty, but this is the answer and the only answer that the scriptures give.
in pure concept, if there is 'god' than 'god' is infinitely beyond man in wisdom, capability, foresight, power and every virtue, or else how could we call him 'god' ? i take this reasoning. i accept it, even as i also wonder how & why it is that the world and life and the human condition came to be as it is. i really think that approaching 'god' with anything other than complete humility is foolish - he could squish me like a bug, erase me like a doodle, throw me away like a cigarette butt and there is no higher authority or justice i could appeal to other than 'god' himself, else he is not 'god.'
yeah, that's fear, and it is distasteful to mankind's nature to humble ourselves like that, especially before an ideological construct, but this is because our nature is proud - which the God of the bible calls sinful. pride is the original sin of Satan, and is #1 on the list of things God hates - above porn & murder and slamming someone into a locker. that this book says God hates pride more than anything else is in itself interesting..
but setting that aside - i think already most of what i've said here appeals to God being sovereign - how can a human be sure that divine love is genuine?
how do humans prove their love to one another?
imperfectly, for starters, haha.
but if i love a girl and i want to show her that - i might give her gifts. roses and chocolates and puppies! hasn't God done this for us too? we have sunsets and all the beauty of the earth, all the good food and the warm sunshine on our face, and guess who created puppies and kittens in the first place? the universe certainly didn't have to be this way. you can look at it as the anthropomorphic principle, but still, there it is, a universe full of beauty and wonder, and things that make us smile exist in it -- smiling exists.
if i love a girl i would be patient with her silliness - God too is patient; the same things we could say demonstrate His uncaring from a judgmental perspective demonstrate his patience from the perspective of faith. is he uncaring to let men go on doing wicked things without punishing them, or is He patient to give wicked men every opportunity to turn from their wicked ways? (are we even qualified to answer??)
if i love a girl i would put off my own plans to do the things she wants to do. here too, we could question God's character when we don't see what we could understand as his perfect will being carried out, or we could understand this as God allowing mankind to do their own thing - where the bible teaches that man's "own thing" is to do wickedness, that 'the heart is deceitfully wicked' - this again speaks of patience on God's part.
if i love a girl i would sacrifice myself for her. i would lay aside my own ideals, forgive her where she falls short of them to accept her, but hoping and working to patiently help her to enrich herself and become the best woman she can be. i would even die in her place, and leave her all my treasures. this is what Jesus has done.
if i chastise her, it would be like a father who fusses at his daughter, because he knows what is best. the way a daughter knows her father's fussing was from his love is that when she has grown old, she learns how her ways as a child were foolish and sees by experience that her father was urging her towards wisdom. while she is a child she cannot understand these things; she can only trust him. (yeah, here i am back at sovereignty again!)
i think we have to admit that cosmically we are children. God's love for us then must be like a father's love for a child, and that kind of love from a child's perspective isn't always clear. human children are finicky and selfish; when their fathers give them toys and candy and hugs, they don't doubt love. but 30 minutes later when they are fussed at for leaving their candy wrappers laying around or playing with their toys when they should have been finishing their homework, or told to eat their vegetables and to brush their teeth, children say their fathers are the 'worst parents ever.' obviously an outside observer will see that the child's judgement is founded on unwarranted pride and incomplete information, and children able to recognize that they are childishness and trust their fathers are able to understand in time the love their fathers show them.
Christ also calls the church His bride - and in the old testament God speaks of Israel as both His adopted daughter and as a wife he took in, who became a whore, but whom after justly punishing and cleansing her, He was willing against the prevailing worldly wisdom to take back. so His love is even more than a father to a child, but as a husband and a wife. this love we cannot understand until we accept His marriage proposal. the love between newlyweds or a couple wooing each other or engaged to be married isn't near the depth of the love a couple celebrating their 50th anniversary share. all the doubt and confusion and amazement of the early years turns into trust & unspeakable understanding & thankfulness as time passes by. so too with God and man, taking the initial steps requires faith & is done with trepidation and anticipation, and looking back through hard times and stress, we wouldn't trade it for the world.