Have Diabetes. Done Toe Amputation For Non-healing Shoe Bite. High Creatinine And BUN Level. Need Help

Hi, I am Raghav from India. I am having concern in regards to my dad health complication, In detail as follows. My father is 66 yrs old and he is diabetic Patient past from 15 yrs , His Sugar level was not maintained properly as he use to work in railways (lot of traveling) he never had any problems, Until last three months. He had small slipper bite on his right foot on the toe a blister like , After 20 days of treatment there was no improvement later as last option Toe Amputation was done and after 4 days we found secondary Infection(because of not proper treatment/medication or dressing ) when consulted to Treating Doctor , i was told his kidneys are not in good condition per reading BUN was 74 and Creatinine was 1.9, Later the day symptom were close to Septicemia( Swearing /vomiting/ cough . Finally we took him for second opinion; with other doctor his BUN and Creatinnie gone up to 124 and 4.4 within 4 days . Next move was his above knee amputation where i had signed for DIL and no guarantee was given to his life, Post Operation, He was unconscious for Three days with god grace he was back and stable but his BUN and Creatinine was at 100 and 2.4 when discharged. With Dr Advise i stopped giving Salt and Protein, after 15 days Now Is BUN and Cretine is 36 and 1.6 respectively. Please advise on this and Other problem post op , as his vein were hard to find for injection hence Venisection was done on left leg and its nearly 45 days still not healing and other thing is his Urine Catheter sis not removed we tried once in-between he was not able pass it thru Please Advise on this as well, i have tried my best to convey the Scenario, Please help me out with best advise