A few thoughts....
1. I did thought exercises long ago based on a future with almost 100% automation - a UBI will be necessary - the problem is what do people do with their time that gives them long term life satisfaction? It’s a difficult question.
2. I don’t think we will ever see deflation again. Now that the government can just create money out of thin air and send it directly to the end user digitally bypassing bank, they can prime the pump of inflation any time they want.
3. I think your productivity gain predictions are really high in the near future. Perhaps in 50 years. There are still a lot of improvements to be made in the manual labor side of the equation, as well as the review for accuracy side of the equation.
4. The tools will allow the top 10% to really flourish, while those below will depend on the redistribution from the 10%.
5. Porn will become almost 100% fake.
“UBI” would be a misnomer, just UI - to the extent that robots eliminate scarcity, there will be no reason to limit “universal income” to “basics.” Elimination of scarcity would call the very idea of economics - and of money as we know it - into question. But it would seem that, in the industrial age, “plenty” has always been a moving target. People might protest that their own yacht is smaller than that of Bill Gates . . .The fundamental issue of such a future is the theory that it would cause people to deliberately break it just so something unexpected could happen. This issue was identified over a century ago.
In future there might be a Neurolink app for that . . .