I would err on the side of caution were the pre-load is concerned. The standard bearing surface delamination is almost exclusively caused by too high a pre-load of the bearing.
When I set bearing pre-load, I do it by feel. I'll tighten the adjustment until I can feel zero play, the a fraction more. I then do what I call the "spin test". For this test, I spin the shaft, and see how long it takes to stop rotating. Basically I like it to spin to a stop in about 1/2 to 3/4 of a turn. If I'm happy that I've removed all free play, and there's an amount of drag on the bearings too, then I'm happy.
The factory pre-load figure seems excessive to me, which I believe it the cause of the bearing failing in the first place.
Maybe try a local clutch clinic to see if they have a correct sized old clutch plate you can have.