>That seems like a population that would be pretty hard to keep going without having a few extra Earths.
Do you think this problem is merely very difficult, or literally impossible to solve (e.g. because of some physical law)? I think that if a bunch of really smart humans tried really hard to solve this problem, and you predicted very very confidently that they would fail, then I would be pretty skeptical of your confidence. Just as an example, you suggest getting some more Earths. Sounds like one solid approach; expand humanity to other planets!
>We are all going to die someday and there is nothing we can do about it. [...] I don't believe anybody will ever find immortality (at least not in this life).
This might literally true, in the sense that we probably can't survive the heat death of the universe in however many bazillions of years. But do you think it is implausible that advanced medical technology could e.g. keep us alive, healthy, and sane for, say, thousands of years? This sounds both plausible and quite desirable to me, and I'm confused by your statements---for instance, I can't tell whether you are making a factual claim or an aesthetic claim.
>The people seeing cryogenics are largely snake-oil salesmen.
Eh? They seem pretty sincere; the people who run these organizations (Cryonics Institute, Alcor) are generally themselves signed up for cryonics, and speak passionately about life extension as a desirable goal. Cryonics is not exactly a get-rich-quick scheme.