JustHuman: I can accept that within God's realm there can be true free will, providing He doesn't mingle too much in our lives.
Actually, if God gives us ANY freedom to decide ANYTHING for ourselves, then that is a measure of free will. But although our free will given provides us a wide measure of freedom, it still isn't unlimited. If it was unlimited, man - the worst and evil amongst us - would have been able to bring destruction upon the entire planet. Our evil ways are restricted, and are only allowed for a time (this lifetime). Having a severe deficit in knowledge, and being sinful creatures, out limitations, so imposed, are a GOOD and merciful thing!
JustHuman: But to what purpose did God create us? Not to give Him some company, admiration and love.
As for "company, admiration and love" - no, He does not NEED those things. God is complete within His fellowship within the Trinity. He has no deficits of which new creations would make Him more satisfied, happier, more complete, etc. - these are human pursuits. God is a creative Being Who loves to create. He created us because that is what He wanted to do. But the magnificence is, for those saved, we, though created "things," will be more extraordinary that we can ever imagine. So, God is a creator of incredible things - whether transforming the sullied (per sin), or creating the beautiful things "from scratch" (from nothingness).
JustHuman: To become a child of God? To live (for the lucky ones) an eternity in a never-changing heaven?
There is NO luck involved! God specifically placed people in time and geographic place, family circumstances, so that those so willing would become saved. However God decides to initiate and complete that salvation with those who will not permanently resist Him. There is a God-given choice that all men can make (per their free will) - they can seek God, or they can run from Him (and creating man-made religion and gods is another "clever" initiative of man designed to create gods they are comfortable with serving - or rather, that ultimately are thought to serve the spiritual needs of the creature. The REAL God desires man serve Him. But HE is the One Who leads such understandings of Himself, from His loving nature. Before God created man, He knew all about the Crucifixion and suffering He would one day do for man (actually, He's ALWAYS known of that). He created a world that has an ability to reject Him - and it's the very same world He (Jesus) subjected Himself to.
JustHuman: And why is living in a materialistic universe 'pointless'? Meaningless?
Because one cannot know true peace or contentment through material things. We were created with a part of our being that would feel and sense a growing incompleteness, restlessness and dissatisfaction without a relationship with God to fill that emptiness. We can seek all manner of materialism, sensuality - all those things - and still be miserable and unfulfilled in our spirit. We were created to seek God. Why do so many people society admires - the amazingly beautiful, wealthy and successful, so often commit suicide, ruin their lives would chemicals or alcohol, state they are so unhappy? Because they bought into the lie that some level of desired "things" will make them fulfilled. And then they get achieve such things, and realize it's all one big lie. And once they realize that - they often just try different, subsequent "things" - yet with the same resulting misery. Once they realize they cannot become at peace, these things become meaningless, constant reminders that there is not peace to be had through such pursuits.
And the older people get, the more they begin to realize that there will be a day of either decline or some sudden end - in which the best things of this world will either go away for them (their health and youth, material things, etc.), with nothing to look forward to but decline or an end - and often a slow and difficult one. So, for many, they just try to "party to the end" - looking for comfort amongst "stuff." Or they medicate themselves to cope. Before, they'd always looked for some future accomplishments or things they wanted to obtain or do - and then they begin to realize such things will never happen. And so, they lose hope for anything of meaning to themselves spiritually. You can't fill that emptiness successfully except with one thing: God! Those who learn this lesson and seek God have gained wisdom. The rest try to ignore there is a lesson to be learned - or, they just tell themselves, they just don't have all the right "stuff" yet. But "stuff, wealth, fun, sex" - these ultimately turn out to be futile distractions that don't solve the problem.