Your skin problem sounds like psoriasis, you need to put psoriasis cream on it from drugstore or prescription, also use psoriasis shampoo. Better take good vitamins also, it helps. Get checked for swollen prostrate gland. That can also cause problems with urination. Could be bladder infection also,
The urinary problems with yur thirst definitely seem to point to diabetes. Dieabetes can also cause sores on the skin and them not to heal quickly.
Rather than the blood fast test, the glucose test may give better results. Also a HgA1c (or HbA1c) blood test would show the doctor your average sugar levels over a period of 3 months, rather than whether you are diabetic on the day the bloods were taken. I had a glucose test done and I was found as being glucose intolerant. Drinking a small swig of the glucose made me extremely thirstly.
The other condition that can also affect the urinary flow is prostate problems, so it would be worth getting that checked out. If you eat a lot of salty and sugary foods, these can make you feel thirsty too.
With the dry areas, this, does sound like psoriasis. Some people only get red blotches, others get dry mounds of skin like you do. My cousin aged 63 has had it like cauliflower florets. Hie is on an injection med for it and is like a new person now.
If you have not already had yur urine tested, then that may be a good idea to rule out any urinary tract problems. Or have a blood test for kidney and liver function.
You may also be lacking in vitamins and minerals. The one that I have heard that causes cracking dry skin, especially on the lips is Vitamin B12. Your doctor can do a blood test to see if you are low on that, but you can also buy it at the herbal shop. These are Vitamin B12 sublingual small tablets that you place 1 under your tongue.
Some people do not absorb the Vitamin well in their gut, so it may be worth your doctor checking you out for blood related disorders in connection with low levels of B12.
Hope you get sorted out real soon.
Best wishes.
I was going to say it sounds like diabetes too, but you stated that you've been tested for that.
I have had some of the same symptoms as you as well as many other different ones.
Have you been tested for anything else like autoimmune disorders or a thyroid disease?