Good for you, attempting to save a heritage tree - Johnny Appleseed would be so proud. The tree is probably worth saving as apple trees in historic gardens of England live to be twice that age - but the ivy is a problem. You should cut the ivy off at ground level now and to remove all strands that grow up into the tree. You can wait for one year if want and the ivy you cut now will by then turn brown and be much easier to remove. Also cut the ivy on the ground at soil level and try to roll up the cut ivy growth like a jelly roll, using a machete to slice under the roots. You may want to hire strong backs to do this. Once the ivy is gone the tree will get more light and be less likely to topple in a wind storm. As far as pruning, you can prune in the spring before the tree flowers or even wait until fall. The old apple will never have the trim, neat and tidy shape of a young orchard tree but if you are saving it for historical interest this should not matter anyway. Just remove any crossing, damaged or diseased branches and shorten the longest branches that are way out of line. No need to fertilize this survivor if it consistently bears fruit. I do see how a row of cedars would make fencing hidden, provide shelter for birds and wildlife and tidy up the place but an old apple tree provides winter food and spring blossoms and we all need to provide more blooms for our dwindling pollinating bees and other insects. So I vote with you - try to save the apple tree. Keep growing, Marianne Binetti