I boiled raspberries for short time (few minutes) and gave it into the secondary..
It was like 1kg per 10litres. It tourned out great. I wouldn't change anything.
Dry hop has to be in two stages. First when the fermentation is at about 70% (36 - 48 hours after pitching), and second after fermentation.
I do it like 40% - 60%.
Just rinsing with hot water and as soon as I can notice beer stone, I wash it with lactol solution.
Yes, we have very hard water here in bosnia, lots of minerals, calk especially.