For Nietzsche, the approbation of life comes through Music. But also, you have a few things I would like to discuss upon. I will edit this post soon with more to say.
In Birth of Tragedy N details more or less early on that the approbation of life comes through creators creating a faith and hanging that faith over a people such that the faith serves their way of life...
Creation is Nietzsche's "politics" away from the State (we can see this in The New Idol) and it is creation that is the most valuable life affirming tool. Creation allows the creator to hold up a transfiguring mirror that affirms the demands of their life.
For Nietzsche in particular, we can see from the Birth of Tragedy and the Gay Science that "life is music" and that all the philosophers from Socrates to Kant had "wax in their ears."
In the attempt at self criticism of Birth of Tragedy, we can see Nietzsche details himself at the time of the writing that the book is made up first and foremost from the thoughts and after thoughts of an artist...
This means Nietzsche considers himself an artist as he wrote it. He realized that the book was badly written and changed his angle a bit, to diacuss the affirmation of life in a more universal sense based out of perspective of the beholder. Hence by the time we get to the prologue to BGE we have that "perspective is the fundamental condition of life."
As you've detailed suffering is quite an integral part of N' philosophy, and I have a great quote from N himself as to why suffering is integral, and it's more or less that it itself is transfiguring...
It will be surmised that I should not like to take leave ungratefully of that period of severe sickness, the advantage of which is not even yet exhausted in me: for I am sufficiently conscious of what I have in advance of the spiritually robust generally, in my changeful state of health. A philosopher who has made the tour of many states of health, and always makes it anew, has also gone through just as many philosophies: he really cannot do otherwise than transform his condition on every occasion into the most ingenious posture and position,—this art of transfiguration is just philosophy....It is great pain only, the long slow pain which takes time, by which we are burned as it were with green wood, that compels us philosophers to descend into our ultimate depths, and divest ourselves of all trust, all good-nature, veiling, gentleness, and averageness, wherein we have perhaps formerly installed our humanity. I doubt whether such pain "improves" us; but I know that it deepens us. — Nietzsche, § 3 of the Preface to the second edition of GS.
We can see that suffering doesn't necessarily improve us. And Nietzsche details this further in Genealogy... as slave morality often arises out of those who suffer, and fail to disgest the internalization of that suffering. Where as the noble moralities always spring from the triumphant affirmation of ones own demands... (GoM 10).