@poliakov recently wrote about using app switchresx to reduce strain. I have tried it and must say that with the right settings (half of native resolution and non hdpi option), which on my macbook 15in 2018 are 1440x900 I suddenly can even write and read for hours.
Even when I select higher res (1680) but choose non hdpi option its a lot better. The letters and edges are jagged and my eyes finally have a fixation point.
Do you know what the difference between the hdpi and non-hdpi is? Maybe hdpi blurs or dithers more?
This is still a result after the visual therapy I did, maybe without it wouldnt be so good, but still try it and let me know!