Using creams containing urea 10% can be helpful when the skin is this badly cracked. Use frequently then apply cotton socks to allow it to soak in. Petroleum Jelly is also helpful but very greasy.
I would recommend that you avoid feet soaks, but if you do then use an oil based emollient in the basin. Ensure that you wear comfortable footwear and avoid 'flip-flops' or 'mules' which flap across your feet when you walk.
If you find that you have dry eyes and dry mouth then ask your doctor to run an auto-immune screen. In terms of diet, drink plenty of water and have plenty of fruit and vegetables with a high vitamin C which is thought to help in skin repair. Evening Primrose capsules have historically been used by people with dry skin although significant clinical evidence is not available to support this.