Regarding the 158gr +P FBI loads, I would test them in the gun before jumping to conclusions.
I suspect that the warning against using +P loads with lead bullets may be a CYA measure to prevent shooters from using loads that aren't firmly crimped; however, IIRC the Remington-brand 158gr +P FBI loads I use in my M638 have a heavy roll crimp at the case mouth and a machine-applied "crush" crimp in the case near the base of the bullet. I bet that Remington took these steps to ensure that these bullets will never jump crimp no matter how light of a revolver you use them in.
I would load the gun, fire 3 rounds, inspect the remaining 2 rounds for signs of jumping crimp, and repeat. Personally, if I got through 2 boxes (20 cylinders) of FBI loads and none of them jumped crimp, I'd call it good and carry them.
"Smokey, this is not 'Nam. This is bowling. There are rules... MARK IT ZERO!!" - Walter Sobchak