Nortriptyline is the least of the evils you mention in your post.

I think you should try it and see what happens.

It might make the "dryness" worse, but maybe not.

Do you take a multivitamin daily? One with retinol A in it (not just betacarotene?

Some people don't convert betacarotene well. Mostly those with hypothyroidism. But low T3 conversion also would do this. Betacarotene from food is converted in the liver when thyroid is normal.

Dry skin and mucous membranes may be due to low Vitamin A.

I have been reading about some seniors becoming low in A... it is a new topic being discussed on some sites. It appears that it can be a hidden deficiency.
If you want to try this use no more than 8000IU of Vit A daily for a couple of months and see what happens. I got mine at Target... their brand.
You could also use it in a cod liver oil capsule. But just take one, and don't increase doses...as it can be toxic if abused.

This intervention is taking down my "lupus like" redness on my arms I've had for years!