In 15 years of RB re-builds I have seen some awful repairs and so called specialists turning out some shocking work. I have never seen anyone try to repair the keys ways in such a way. In standard form the RB crank is pretty strong if built correctly cutting corners will ultimately lead to self destruction. As I have seen this many times!
The RB bottom pulley requires a massive amount of torque to tighten it and have many times seen bottom pulleys come off.
The OS Giken RB30 requires slacken and re-torque after first 1000 miles as it produces so much torque in some cases loosens the bottom pulley.
You can make a temporary fix however I think you will eventually result in the bottom pulley working its way loose, or spinning a shell as the crank will be out of balance.
My advice would be to replace the crank with good used, new shell's oil pump (re-build) ...
If you can't then a good short motor...
If this isn't an option then I guess you will just drive until destruction.
Please let me know if I can be of more help
Rich