Yes, Quantum Immortality is "real", as far as it goes. The problem is that it is inappropriately named and leads to inappropriate conclusions by misusing non-quantum intuitions. So yes, if you plan to put yourself in a 50% quantum death-box and keep doing so indefinitely you can expect there to be a branch in which you remain alive through 100 iterations. The mistake is to consider this intuitively closer to "immortality" rather than "almost entirely dead".

As far as I know I am already "almost entirely dead" in all possible worlds, so playing with the scant epsilon of universes I exist in doesn't seem like too much of a problem. If there were a way to narrow my measure of existence down to only a single universe in which only the very best things ever happened it seems like that would have the highest utility of any solution. If such a best universe exists it is very, very unlikely. My expected value from its existence is consequently very, very little unless I can prevent my experience in lesser universes.

The questions are twofold: Can quantum suicide select such a best universe (is there a cause of the very best things happening that involves continually trying to kill myself; it seems contradictory) and if so, is it the most likely or quickest way to experience such a universe? Clearly an even better goal would be a future where all universes are the best possible universe, but the ability to accomplish that does not seem likely. I lack a sufficient understanding of quantum mechanics (and the real territory) to answer these questions.

No. Don't do a count on branches, aggregate the amplitude of the branches in question. We should expect to die. There happen to be an infinite (as far as we know) number of progressively more 'improbable' branches in which we are degrading but they still aggregate to something trivial. It is like a zeno's paradox.

This is something of a paradox because my dead branches won't experience anything, leaving my experience only in the branches where I live. I should expect to experience near-death, but I should never expect to experience being dead. So a more useful expectation is what my future self will experience in 100 years, 1,000 years, or 1,000,000 years. Probably I will have died off in all but an epsilon of future possible universes, but what will those epsilon be like? They are the ones that matter.