Tuomo, I have fought with it as it was and hoped for more agreable version 
. I liked to simulate most strained/thickest ones, mentioned probably in “? Turk Okculugu ?” ( but I have only the picture with the thicknesses of layers ). I did not take into account the prestressing of wood and horn layers by reflexing the limbs throughout the sinewing operation, nor changes in the Young moduli at higher levels of strains. Here is the link :
https://drive.google.com/drive/folders/1MTAyPS7WJrdFSouqTkw2r5codBaR3jgB?usp=sharing
There is also one .xls file with the ( thickness ) summary tables and maximal relative strains in this folder ( if you will be interrested I will translate the headings into english language ).
It seems that cores are still stressed under their breaking strength somehow ?
Yes, I suppose too, that wood-sinew joint is not a problem, because the weakest member is the ( cohesion of ) sinew layer, when overcoming the reflex at first time bending the bow to the tepeliks.