I have no advice on care of the ivy. But, whatever you do, please keep the ivy from climbing the trees surrounding your property and invading the adjacent forest. Ivy can be invasive and will crowd out native understory plants.

I've cared for a lot of English ivy and have never raked leaves off of any of it. The fact that tree leaves don't need to be raked off of it is one of ivy's strong points. However, since leaves blow in the wind, they can heap up in the same manner as snow drifts. Don't allow heaped up piles of leaves to smother the ivy. Spread them out so they sift down into the ivy, not cover it.

Ivy will want fertilizer in the Spring when it begins to grow ... not in the winter when it is dormant.

In spite of the fact that ivy will tolerate some of the lowest light levels of any plant, that doesn't mean that it is going to perform its best inside a cave. We can't see your yard and its light levels, but if you have so much forest cover that the yard is dark and gloomy, that could explain why the ivy isn't gleaming. Consider if you could either raise the forest canopy, or thin it by removing some smaller trees, and therefore, let in more light. You wouldn't even need to let in direct sun, but just lighten the shade. (I'm speculating because we cannot see the conditions.)

Thanks for some good advice. I think our light levels are okay, as the canopy is pretty high, and our neighbors have fewer trees than we. Some of it gets sun for an hour.