So unless we get faster than light travel or we greatly reduce the amount of space into which you can physically cram a living human we are under 13000 years away from a pretty hard upper limit.

Make more realistic assumptions than speed of light expansion of humanity and that limit gets a lot shorter even with growth rates quite a bit lower than 1%.

In a way I agree that the feasible limits, even on Earth, may be orders of magnitude larger (say, in terms of population, perhaps) than we currently have. But the current rate of growth in any case is probably unsustainable because of imbalances like co2 emissions. I do think it's feasible to change to renewable energy in the short term, if only political motivation was a bit higher (please, go out and vote focused on climate change, folks!). If I were to lay out a strategy for humankind, I'd say we should focus on climate change for the next few decades, and then we can resume growing (to avoid possible collapse).

Limits to technology are actually non-trivial due to the atomic nature of objects, limited number of chemical elements with limited range of properties, etc.. Intelligence itself isn't free and keeping the Great Self-sustaining Rube Goldberg contraption working is not trivial. It's very hard to predict what limitations we can overcome -- see Moore's law slowing down. Some limits we've almost reached such as luminous efficacy (LEDs in lm/W). Soon we'll be faced with the question of whether we want to make Earth into a Caves of Steel landscape (ending most natural life to create a hyper-efficient human/machine habitat) capable of sustaining more humans or a Solarpunk landscape (preserving natural ecosystems) with a more limited population. I think there's a large degree of arrogance to the first, because I don't feel competent enough to evaluate the true value of animal lives, supposing a large quantity of animals are sentient, and they have intrinsic scientific and cultural value. I think this requires an exercise in imagination from all of us. In any case, it's probably a great idea if we could at least keep the oceans, rainforests, and major national parks healthy.

One crazy dream I have is to colonize not Mars, but Mercury. In Mercury solar energy density is crazy high. There's even some thermal energy from the solar thermal gradient. You can dig to get to nice temperature ranges and be safe from radiation, all this works well since the planet is tidally locked and therefore doesn't rotate, there's no diurnal variation. You can build a crazy Cave-of-Steel there and live your life in a cramped cell playing video games (or [insert activity]), if that's what your vision of heaven is.

In any case: Hack the Planet!*

*: In a good way, of course :)