Very tart raspberry cider

We made a 3 gallon batch of raspberry cider back in march using 2 1/2 gal of ziegler's apple cider (unfiltered) and 2 cans of Oregon raspberries in syrup (ingredients said syrup was sugar and water). Pitched 1 pkg of Nottingham yeast. O.G.-1.050. We've been at a steady 1.022 for about a week, the ciders starting to fall clear, it tastes pretty good but it's insanely tart. Makes ya take a step back.
My thoughts are to rack it out of primary into a secondary carboy and let it sit for awhile in hopes that the tartness will mellow and the fruit flavor will start to come through. Is this the right idea? Or is there a better way to mellow out an extremely tart cider?

I've never tried raspberries before but it's flavors may blend and settle more given more time. It seems like it could ferment some more too but that may serve to make it tarter.

Back sweeten it to make it less tart. It should have at least mellowed out a bit from a month of aging. Hence why I would backsweeten for sure.

Ziegler's contains potassium sorbate, I'm surprised you got it to ferment at all.

steelcitybrew said:

Back sweeten it to make it less tart. It should have at least mellowed out a bit from a month of aging. Hence why I would backsweeten for sure.

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I thought so for sure. When I did a gravity reading 5 weeks ago gravity was 1.025 and in my notes I said it was quite tart, but not overly so. Now it's overly so! Big time.
I mentioned backsweetening with lactose to my wife and she's concerned about getting a creamy or milky taste. Does lactose do that? Can I get a decent sweet flavor using lactose?
I know I could also kill the yeast with k-sorbate (had no clue ziegler's had that in it, glad it still fermented) and then sweeten with sugar or juice. But swmbo wants a carbonated cider and I only have one keg, and that's dedicated for one of my beers. If I use k-sorbate, is force carbing my only option for a non still cider?
Sorry for all the n00b questions, but this is only the second cider we've attempted.