Diabetics have a lot of circulation problems, and extremities are the first to be affected in anything that involves poor circulation.. I would definitely take time, at least 3 times a week, to do some massaging down along your legs to try to promote the circulation. Soaking your feet in salts can do a lot of good as well (plus the salt helps kill off bacteria and other nasties) and it also softens the feet.. These two can be done together at the same time. (Also, in the long-term of things, exercising helps with circulation a LOT, especially cardio, so ensure you're getting plenty of that in to keep your hands and feet strong and healthy.)
As far as calluses go.. they're good to have. You don't want tender delicate feet. but anything beyond a slight roughness is too much and unnecessary. You should be able to feel a difference in the skin (around your heels, balls, and toes) in comparison to the arch, and it should be slightly less sensitive to the touch (if you're ticklish, the callus should not be as sensitive as the arch, for example) but nothing more than that is really necessary, so any calluses especially ones that are cracking need to be attended to.. so after soaking your feet, exfoliating them off with a stone or other such rough object should help. A sloughing lotion should be applied once a week to prevent calluses from building up. Other techniques to prevent calluses from building up: moisturizers (read: petroleum jelly overnight with socks on) help, frequent exfoliation in trouble spots, and ensuring your boots/shoes fit well and aren't too loose.
The cracking of the feet.. It needs moisture. Petroleum jelly takes a long time to sink in, but if you apply it the night before in copious amounts (like if you were a little kid and 'moderation' was a fancy greek word your parents just used yesterday in front of you) and wear a sock it won't get everywhere and itll have time to soak in overnight. In the morning, if the skin is bone dry and feels no different it means your feet REALLY needed moisture there (read: reapplication the next night is probably necessary). if there's a supple, moisturized feeling to the skin, then it's spot on and only a light lotion moisturizer needs to be applied to those areas (though re-applying the jelly won't harm them at all). If there is petroleum jelly left over, a quick wash of the feet will fix that and it means you don't really need to moisturize the skin at that time, or that it had its fill. This usually doesn't happen though.
I don't know why people don't powder their feet anymore either.. It's absolutely essential if you're wearing closed-off shoes all day. Not only does it help prevent bacteria and fungi, and keep your feet from smelling caca, but it also prevents sweat from accumulating which can irritate your skin and manifest that irritation in several ways.
..I'm definitely late in answering, but hope this helps.
