As you see (or taste) lower temp gives decreased perception of sweetness and increased pick-up of acid/tannin. This is why serving temperature for a mead can be important.
For a cyser that is too tart, a tiny bit of sweetening, just enough to offset the acidity, often works best. However, if you don't like that approach, aging will help, but that can take years. Some folks have put their cyser through a malolactic fermentation to reduce the malic acid. That can create some interesting flavors, but can also wreck your batch. Using some carbonates to reduce acidity works, but be careful not to raise the pH too much - spoilage organisms love a pH greater than 4. Whatever you choose, I'd error on the side of doing less - there's nothing worse than flabby cyser.
Thanks, Medsen. I definitely appreciate the advice. As you probably read, I'm going to wait and see what the oak can do to improve the situation. If that doesn't do the trick, I may consider backsweetening, even though I am rather disposed against the practice in general. One step at a time! What I
can say for sure, though, is that I will not make another cider/cyser using only honeycrisp apple juice. It will definitely be one I use as a portion of a blend of apple juice varieties, though, because it has some admirable qualities. But I've heard experienced cider makers state adamantly that they never make single source ciders. Always blends. Sage advice, to be sure.
Additionally, as luck would have it, a friend of mine just finished a cyser as well, and it stopped dead at 1.070, which is exactly where the yeast's ABV tolerance should have told him it would stop. Although he and his wife
love the stuff just like it is ("KACK!"), I'm trying to get him to donate a gallon or two of it to me to blend with mine in return for a few bottles of the well-balanced product. I really think that's my best option at the moment.