Cool, cool, true that, but also, then your program isn't necessarily better than other programs with so-so weight loss success rates, is it?

But it's the only one that allows people to reach such heights. That's why the people who are truly selfless are one in a million and can only be Jewish. G-d has provided Jews with a soul that can overcome its physical boundaries by revealing itself and cleaving to G-d. However, that comes from only from a person's self sacrifice and eighty years of hard work. I think this should address the second question as well.

tl;dr It's nearly impossible to be selfless but Judaism provides the key points to being so.

God doesn't need me to eat matzah

He does. Chassidus explains that the reason G-d created this world and defined His infinite self into a physical creation is because He wants people to transform it. When you eat matzah, you're not only elevating the sparks hidden spiritually inside but also elevating your soul by connecting it with Hashem. That's the way it connects. Doing Hashem's commandments allows the neshama to find its true self-expression, which in turn refines us a bit more. No one says it's immediately apparent and may take decades depending on the mission the person was sent for, but this is what Hashem wants.

being directed to more sources.

Chabad Chassidus was an eye-opener for me and continues to be the way I direct my Yiddishkeit. Everything I've said is explained by Chabad Chassidus. There are literally thousands of Chabad Chassidus books, despite being only 250 years old.

there's been lots of persecution and stuff that have interfered with the steady transmission of the mesorah and plenty of things can have been lost along the way, especially during the immediate aftermath of the two big exiles.

I'm not big on history but I think there have been Rabbis in every generation who loyally transmitted what they've learned. It's literally against their nature to be affected by the environment (see above answer about special souls).

I mean, that's nice, but the world isn't 6000 years old.

It is. The Torah says so and the Torah is truth. Otherwise, as it's another absolute, we can begin to disregard everything else it has said. Besides, G-d could have created the world billions of years old, which is the crux of the Lubavitcher Rebbe's argument.

what's the book about?

Responses on science. Jewish scientists usually wrote to him with their concerns of faith. The letters are long, thoughtful and backed by scientific data of this century.