I can understand the complexity of your father's health problems and your helpnessness. You can try the following owing to the limitations he is having:
1. Due to limited mobility, I would suggest him to do some arm and chair exercises which will help in lowering his blood sugar levels. You can learn about these from a physiotherapist or from web searching also if a physiotherapist is not available.
2. Check his blood sugar frequently before and after meals to adjust food intake with
insulin dose.
3. Cut down on the intake of calories from fats and give him more fibre rich foods like whole fruits, raw vegetables as salads and whole grain cereals like whole wheat chapati, broken wheat porridge or dalia, oat bran, wheat bran added to foods will help in lowering his total intake of calories thus lowering his sugar levels.
4. Check his feet daily for any cuts, blisters, bruises and ulcers and see a
foot care specialist for further treatment.
5. Control portion sizes of food and give him small frequent meals to prevent blood sugar spikes.
6. Avoid skipping meals or staying hungry to bring down sugar levels as this will harm him more than doing any good.
7. Make sure he includes adequate amounts of
proteins from pulses/legumes/beans and if non-vegetarian eggwhites, lean meat, chicken and fish can be taken.
8. Avoid giving any sugary foods, fried foods and nuts and dry fruits due to their high fat content.
9. Choose low fat milk/curd and cheese.
10. Apply some
aloe vera gel to heal blisters. Ask him to wash his feet in warm water and soap and dry it with a towel. Apply a good moisturiser to the feet to prevent dryness. Inspect feet daily after washing for any skin changes.
Hope this will guide you in helping your father manage his health in a better way.