an unglazed clay pot ... is an indoor nightmare.. in my experience ... i gave up on them decades ago .... they are for greenhouses.. even outside ,... they are a PIA ... find a plastic pot of exactly the same size ... and repot it ... meaing.. slip it out.. and right back in ... the pot is wicking water.. out its sides .... so your media is drying in a weird way .... causing the plant to struggle ... it should not need too much water in winter.. indoors ... i water my ivy [whatever type it is] about once a week ... and its bone dry by the time i water again ... one hour in a north window.. will NEVER be defined as too much sun ... you are probably also not thinking about how the window panes themselves.. cut the effectiveness of the light ... and IMHO.. an ivy does not need more light ... i highly doubt a winter window is 70 night and day .... but in your z7 ... its not really an issue... i got up this morning in MI to NINE DEGREES .... you could feel the cold within a foot of the window ... but again ... it shouldnt matter in z7 ... its just not an issue .... since you are new.. i am just ruling out.. some of the things you listed .... the furnace/air movement.. is complicating the wicking on the pot ... though i doubt your furnace.. in z7 ... runs enough to affect the plant all that much .... up in my MI .... the furnace runs so much in winter.. maintaining humidity can make for leathery leaves on this kind of plant ... but the house humidifier deals with that ... if you buy the right size palstic pot ... you can slide the plastic pot into the clay.. if you like the look ... a glazed ceramic pot would not wick due to the glaze ... but i still have problems with those ... and part of it.. is how cold they can get at night.. as mentioned above... if the roots mass gets cold.. and it cant recover/warm during a real cold day .... the plants can go into SLLLOOOWWWW motion ... which a lot of them do in winter anyway .... [its also because the sun is so low in the sky.. light levels have fallen] and of course.. cold wet media... can lead to root rots ... etc ... but then.. i tend toward really dry plants ... so i avoid such.. along with the critters [fungus gnats] one of the best greenhouse growers near me.. lets all his plants wilt.. before watering them ... says it forces them to thrive thru growing a solid root mass ... but he is a professional ... his things WILL be watered... the evening of the day of wilting .. but then.. he has perfect humidity.. and all other variables ... point being.. a little wilt.. is not much to worry about .... as to your book comment... 10 years from now.. you will probably go back and read them.. and realize its all there ... if you only knew then.. what you know by the time you reread it .... anyway.. to my reading.. everything you are doing is spot on.. except for that clay pot ... good luck .... try to enjoy the process ... and not worry.. nor love your plant...

Believe it or not, there are several diseases that can affect English Ivy, under the right conditions (for the diseases, that is). Your University of MO Extension service has a plant diagnostic laboratory available for the testing of plant problems. I'd call your local extension office for assistance in packing up some samples for culture. I expect that the local office is required to fill out the paper work and send the samples from their offices. Here is a link that might be useful: Lookee here!

I have several English ivy plants indoors, but they are just sort of hanging on (a bit leggy looking), even in the west-facing window with plenty of light. They are loving the cooler weather, though, and I've noticed more growth now than in the spring and summer! Isn't that weird? The spider mite thing is tricky. I do run a humidifier, so I haven't had as much of a problem as others. Also, every time I water, I gently spray the leaves to rid of any dust or pests. Like others said, this plant is probably best outdoors on a trellis or where it can be controlled. Personal opinion: I would not want to constantly be bringing this plant from indoors to outdoor and vice versa, since that is a nice way to invite the dreaded spider mite into your home to hitch a ride on your other plants. : )

It's not a bad idea per se, just a pointless one!! Nails - copper or otherwise - will not kill any plant. That is a gardening myth!