On your question about which caliber is best.
A 50 is best for Sabot [45 is also good] and because of recoil I would say they are better for conical.
The 54 is the long range round ball gun it has a much better BC and foot pounds of energy while still being light enough to load up to 2000 FPS.
Some like a 58 which is a hard hitter but uses a ball that is heavy enough that the recoil would be bad if you could get them to shoot at 2000 FPS and the twist in any of the commercial barrels is not designed for high speed a 1-100 would be about what I would want.
The safety issue will always be a problem with CVA because of the names past history,
they make some decent guns now. Don't believe that it was only inlines that had a problem the one that put shrapnel in me was a side lock.
It had a laminated barrel and was not over loaded.
The better companies use a sonar test to eliminate that problem. If you are not comfortable with that barrel take it to a good gun smith to be checked if it had much rust on it have it checked or if the bore is rough you might consider a new barrel.