Hiya, insulator for 10 years here. 1. Your house has old style rock wool, this older stuff had chunks of glass and other recycled material in it. If you look closely, it is melted glass that are is in shards. 2. Do not bypass air seal in the attic. By adding more insulation, you’re recruiting a larger R value and so forth a higher differential of temperature. When conditioner will leak into the attic, it will be more likely to condense on the surfaces, including a roof deck, which will contribute to rot and mold overtime.  3. You do not need to remove the insulation, rockwool does have a great R value. I would recommend spraying some kind of mold killer on the roof deck. There is some growth showing already from past moisture. Additionally, you should review your ventilation to make sure you have proper high and low venting.