The cam repair is prbably a spray weld hard coating. It might work if you are broke, I understand that problem. A good auto machine sop should be able to help and press in and peen your new cam followers.
Don't give up.
This is the bad luck.
The engine really is tough.
Use the magnet on the top end and change the oil in the lower end, use cheap stuff, run it for a bit and change it again. I would just do the lower end oil, not the main tube. It is filtered to get in there.
Finially you can change everything and the filters and use good oil.
'02 KTM 640 Adventure-lowered
"On the road there are no special cases."
Cormack McCarthy-The Crossing
The faster it goes the faster it breaks.
And high performance=high maintenance.