Ignoring the whole north-facing, dark room issue for a moment. How do you want your family room to look? Whatever you end up with, it has to be something that you like, not just what designers say you should do. All the color advice in the world is useless if you don't like the colors, shades or tones recommended. So my gut feeling is that if you mostly like creamy walls with white trim, then that's what you should do in this family room, instead of trying to embrace darker colors. Creamy, warm, white walls will certainly brighten this space, while darker walls may make you feel it is too dark. Short-term, a lighter colored area rug or two will brighten up the floor and make the room seems brighter and airier. Long-term, I'd invest in more lighting. Two chandeliers, if the room size is large enough. Wall scones, definitely. And a few floor and table lamps for task lighting. You've got dark floors. Stick to light colors on the walls and mid-tones for the furniture. I moved in to a house with one room painted a dark, navy blue. It wasn't cozy, it didn't warm up the room. The color just made the room dark. And no matter how many lamps I added to the room, the wall color just seemed to soak up all the light. It was either paint, or saw the room off the house. So my advice is that if you like light-colored walls, putting up a darker color in an already dark room will not work for you.

50-ish, if you find one at 45 or so that you like don't discount it just because of the LRV number. Unless there are standards/color specs involved, LRV is more like a loosey-goosey guideline, not a formula or prescription to follow. And, yes, colors with a higher LRV number have better odds of delivering the light and airy atmosphere you're after vs. darker colors. A dramatically shifting paint color has more to do with its own metameric tendencies vs. the quality of light. A rule of thumb is if your color stays consistent in appearance when viewed in fluorescent and incandescent lighting, it will *probably* be consistent in any light source. More about north light: North exposure is not direct rays of sunlight. Very different from south light beaming into your kitchen almost all day long, or the morning sun bursting through your east facing bedroom windows at the break of day. North light isn’t necessarily reflecting or bouncing off of something else to get inside the space, it’s just that when your windows face north you don’t have actual, direct beams of light entering fenestration. North light is the most balanced from a spectral distribution perspective, it has a nice, even collection of all the wavelengths though it tends to be heavier in the blue range. Because it’s a balanced bundle of wavelengths and also because it is not a direct beaming, or spot-light effect of natural light, north facing rooms are ideal for any kind of artistic work environment. The pronounced blue of north light is a factoid that's been blown way out of proportion. Blogosphere has taken that one single aspect of north light and made a huge deal out of it - I guess because it makes a good 'sound bite' or something. I dunno. But it's kind of a dumb thing to hyper-focus on. Heavy in blue doesn't mean it's gray. Doesn't necessarily mean it's cool either. North light is simply indirect light that's balanced over the visible spectrum as a whole but with a pronounced bump of blue.

SW Alabaster is lovely light iff white but it is in the Yellow Hue family and that core characteristic in North facing space could show more predominately. I would need to see your furnishings and rugs plus better pictures of the flooring to make a better informed choice for you. Lots of great off white choices but good to understand what you plan for the room.

First make sure all your lighting is the same I like LED4000K but you can do 3500K then choose wall color understanding that everything in the space affects wall color so post pics of the spaces after you get the lighting done.