that burning on the leaves will be from the lime in the ash,i use smashed up cured bone for my phos if i want to keep it organic,as for the bugs i find most of them piss off when the buds come for some reason,may just be the evil looks i give them, a good way to get those snails is beer,cut the top off a beer can and bury it til its at groung level and put a inch or so of beer in the bottom,the cruise into the can to get the beer but end up getting pissed and drowning,also put a trail of half crushed eggshells around your mound they wont cross it.
Sorry to hear about your climate situation man,it is muuch the same here in some parts of new zealand,alot of people here cross blue berry into the local strains because it is waxy and resists mold and budrot well,another way we combat the crappy seasons is adapting the strain to an area which is what you will most likely what you will have to do to pull off succesful crops in estonia without a greenhouse or a shitload of luck, i sugest starting with something like a ak47 x blueberry or bigbud x blueberry if you can get em or something people have grown successfully in you area,plant as many seeds as you can get hold of and plant the lot, as they grow kill all the weakest and any herms,ideally you would start with 100 and cull down to 5 or 6,hopefully you get a shitload of seeds,if you repeat this 2 more seasons you will have an acclimatized strain that will grow well in your climate,this is how the strains they use on the west coast of the south island of new zealand were acclimatized and it has 2,875 mm averagae yearly rainfall