Specific Gravity varied widely after topping up.

Gray is positive plate material that has been shed. It's time to go whine and plead with your distributor. The sediment sump is probably packed with this material.

An amp hour meter is an excellent indicator of overcharge. Batteries that are supposed to be on maintenance float require "X" amp hours over a given period of time to maintain full float charge. Any increase in "X" warrants an investigation.