To answer question 1: I believe if you mapped out the bad sectors after reformatting, it should be read as a brand new replacement disk and shouldn’t get any errors. If it does, maybe something may be physically faulty with that drive and will have to be replaced with a brand new one.
Question 2: I am not sure if the bad sector would get ignored by ATTO control, but like I said, if you mapped out the bad sectors, it should be read as a brand new disk and should be part of the RAID getting ready to see incase one other RAID goes bad, the extra blank disc can be use to duplicate and back up another drive that can become faulty so you always have the backup of the important data. Thats what I believe. I am pretty new with the ATTO control myself but I have studied RAIDs before and its really good at backing up data between multiple hard drives.
Question, since you said that you are on your third replacement, how often does a drive fail in a raid and do you know the cause of the bad sectors on them?