Yay on picking a landseer!!! We're hoping to add a new landseer pup to our family in February or March, and have found a breeder in NL with whom we are comfortable. I have never dealt with a breeder before, but found that she was very willing to engage with me - she called me and we are spending time getting to know each other. She also sent me her contract and has laid out very carefully what her terms are - all of which are things that we did with our first landseer and he had absolutely no hip or joint issues at all. She has readily provided references and is registered. I can't help on the questions (others are much more experienced in that area) but I can encourage you to make sure the breeder is forthcoming with any and all information you want or need. If they hedge at all, I'd walk away. You're investing more than money here - you're investing your heart, as you already well know.
So sorry for the loss of Dilbert.
Sandy