Which is the problem of the idea. Any kind of thermal engine, such as a stirling engine, would beat this idea in efficiency with those kinds of temperatures.
Inflation "smooths out" the curves in space-time by stretching space out in an exponential manner. So any curves get flattened until the universe is effectively flat. An inflation-like theory that doesn't stretch space out that much leads to its own mysteries.
Which would be the third time in nearly 4 billion years. Still pretty unlikely. Both second and third examples are with an organism that already achieved the eukaryotic stage. It's still not clear if the original shift was a likely event.
Twice, not three times. And the second in an organism that already achieved symbiogenesis. All of this took around 2 billion years or so to happen.
It is a potential great filter candidate, but we only have a sample size of one. So if it turns out the above set of events is rare, then the prokaryote-eukaryote transition would be a major barrier to intelligent life.