"It's only below the knees and goes to ankles and not feet."
When itching occurs below the knees it usually a sign of poor circulation. Peripheral vascular disease is the medical name given to a group of problems that causes poor circulation to the legs and feet. Better control of his glucose and NOT living a sedentary lifestyle helps, like performing daily physical exercise. The alcohol consumption, "4-5 mixed drinks of whiskey", only compounds the problem.
One thought that comes to mind is Atherosclerosis, thickening of the arteries caused by diabetes mixed with alcohol consumption. Google it.
"..the rash is little red bumps that sometimes itch."
Scratching, it seems, has caused an infection. He might try using antibacterial soap, showering in warm not hot water, and applying a good moisturizer like Cetaphil directly afterwards.
I'm no doctor but to Rx Zyrtec and "steroids" is masking the problem not resolving it. Zyrtec is an allergy med [hay fever] and steroids, well, I don't have enough time to write my displeasure about roids.Perhaps someone will come along and add to this thread their itching leg experience and tell us what they did to resolve the itch.