I have the crankshaft in the grinding shop for study and evaluation of a possible repair, they have not assured me anything, I'm waiting.
Regarding the oil flow inside the crankshaft:
Through main bearing number 3 and 5 (green arrow) the connecting rod bearings 2-3 and 4-5 are lubricated.
The main bearings numbers 2-4-6 (red arrow) are blind.
Main bearings 1 and 7 (blue arrow) feed connecting rod bearings 1-6.
I checked them all with a syringe and WD-40, nothing was clogged, if I didn't lubricate connecting rod number 5, the damaged one, I wouldn't lubricate number 4 either.