Your short growing season is one drawback for my favorite blacks. Another may be the amount of moisture. Temperature is also a limiting factor.
My favorite blacks are all mid to late season tomatoes. They also like plenty of sun and a little more heat than I remember growing up in Forest Grove, Oregon. If I remember correctly, by June it was the dry season, so moisture may not be a problem. Cracking fruit can be caused by too much watering. Overwatering will also 'wash out' flavor. Do you grow in ground or in containers?
While I have very good luck with Cherokee Purple there are others I might recommend. Cherokee Chocolate may be an alternative to CP. I also like Carbon, Brad's Black Heart, Bear Creek, J.D's Special C Tex, Spudakee, 1884 Purple and Big Cheef.
Shorter season choice may be the mentioned Black Cherry. I do not like cherry tomatoes but this one is very good, a black in flavor and is quite prolific. You may like some of the new dwarf varieties from the International Dwarf Project: Tasmanian Chocolate, Sarandipity, Dwarf Wild Fred and Dwarf Wild Spudleaf.
I have had no luck with Black Krim or Black from Tula or Black Seaman. That may be my location more than the variety
