Is green growth or degrowth the best near-term future? 

This is about to hit part of southern Asia within 50 years and thus 1-3.5 billion - up to 1 in 3 human beings. https://www.pnas.org/content/early/2020/04/28/1910114117 

To be clear, that article only forecasts that outcome in the "business-as-usual" approach  which seems to mean to them an increase of 5–8 degrees Celsius (figure 2B), which seems like a really high estimate; is that within the standard forecasted range, or is that more like the "assume all progress in renewable energy magically halts and we continue on as if nothing bad is happening" forecast?

1. How much suffering different environmental problems will cause is, as you know, difficult to put numbers on, especially in combination.

I think there is probably a range of decent estimates out there about mortality/DALYs as well as some economic costs under different scenarios (which should not include what I described above, if I understood what was meant by "business-as-usual"). It doesn't need to be precise to be helpful here; even an order of magnitude range could be very helpful, possibly even two orders of magnitude.

2.   Ok, it’s only a 3 minutes text with different aspects, but perhaps like this? Key point: If we continue to have overall GDP growth in rich countries this decade, we will most likely exceed the planetary boundaries even more. Is it worth that? 

The estimated reading time on each post is only a loose estimate, and in this case it definitely was not a 3-minute read for me since I had to re-read multiple things to get a clear picture of what you were vs. weren't claiming + I had to read about some of the mentioned concepts, such as "planetary boundaries." Ultimately, it's just a good practice to have a tl;dr up front that summarizes your main points in 2–4 sentences.

As to the summary in this case, I would again re-emphasize my points above: I'd like to see actual rough estimates as to the potential costs of not pursuing degrowth, because "exceed the planetary boundaries" means basically nothing to me (and even what I briefly read was not very persuasive, especially if we're already exceeding the boundaries and not facing mass starvation/heat exhaustion/etc.)

we should prioritize the environment and other central societal goals and then GDP will be what it becomes. But we don't have a common word for that?

We don't have a term for "Environmental protection"?? That sounds like a failure of imagination. Even an acronym or "no catchphrase at all" seems better to me than "degrowth," which really seems like a counterproductive label.

4. Absolutely in some areas for a limited time, but on a global level we only see some relative decoupling between GDP and climate emissions, no absolute decoupling. Both climate emissions and GDP are globally higher than ever. When it comes to GDP and material footprint we see no global decoupling at all. See figure 1 about this paragraph: 
https://www.eea.europa.eu/publications/growth-without-economic-growth 

To be blunt, that's a rather shallow, self-confirming collection/interpretation of data, especially since it doesn't even grapple with the ideas of the EKC: you shouldn't expect an aggregate/global decoupling when you have numerous developing countries with massive population sizes (China and India) as well as many other developing countries going through the low-income industrial/manufacturing stages currently. A more dispassionate review of the data would look at things with a more granular lens, which is what I did with some WorldBank data for a class paper a few years ago, producing the following graphs:

When something becomes more efficient, we buy more instead of choosing more free time (rebound effect). Of course, it’s not impossible that it will be different in the future, but we need to drastically reduce our environmental impact now, otherwise we’re exceeding more tipping points that can’t be reversed, like losing most of the Amazon rainforest.

Counterpoint: If you replace coal plants with solar or other renewables (e.g., hydroelectric), you don't just adjust your consumption patterns so drastically as to make solar/etc. pollute as much as coal.

More broadly, it just seems like you aren't familiar with the research/argumentation on the EKC. If that's true, I would strongly encourage you to learn more about it if you are planning to focus on environmental concerns. The EKC is certainly debatable in terms of how powerful it is and whether it will act fast enough, but the theoretical evidence is very strong for some activities (i.e., replacing coal with renewables or at least natural gas), and some shallow review of the data (e.g., above) partially supports the idea (with some potential exceptions, such as with oil-producing economies).