Still can’t get over guilt of dog’s death

I have posted twice before over my 16 1/2 year old chi mix who passed away from bladder cancer (which metastasized in Aug 2021) last month. I am seeing a counselor but can’t get over these overwhelming feelings of guilt over decisions I made. As I said before, he had to eat a prescription kibble starting Aug 2020 due to pancreatic, gall bladder, and kidney disease and these kibbles were large and he swallowed them whole. I tried mixing them with broth, oatmeal, and baby food but he wouldn’t continue to eat them this way, just ate them dry. (I don’t know if he had a tooth problem as he was too sick for a dental but his teeth didn’t look too bad as I did brush them. He was missing premolars on one side but had all his teeth on the other side and all his molars. He had chewed some other type kibbles in the past though) He was diagnosed with bladder cancer Nov 2020. He progressively lost weight especially after August of year 2021. He went from 12 (bit overweight) to 9 pounds and was very thin at the end. I was free feeding him starting in Feb 2020 because he ate when he felt like it, but not monitoring how much he was eating ( he was eating, but progressively less). I also gave him oatmeal, veggies, and fruit but not enough for full meals. He was 11 pounds (his desired weight for his size) in June 2021 and the vet was surprised how good he looked so I thought I was doing the right thing. In retrospect, I should have broken up his kibbles (I stupidly was afraid to change anything and have him stop eating and he seemed to be eating them ok, no choking or vomiting, just a little slower as time went by). I should have monitored how much kibble he was eating (I was just happy he was still eating). By looking at my food order after his death, it was not much especially starting in Sept 2021. I should have asked the vet (who he saw every couple months) if I could make his meals and feed him that instead of the kibble (I was so afraid of aggravating his other issues. He could die if he got pancreatitis). At the end he was really skinny. He was always excited about people food until his last couple weeks and I know he would have eaten more than I was giving him but would probably stop eating any kibble at all which I guess wouldn’t have mattered because he was eating only a small amount anyway. I had always made sure he ate all of his life but never really worried about it because he had a tendency to put on weight. If I had monitored his food intake and calories better he probably wouldn’t have lost so much weight. If I had given him food he liked better he would have eaten more. How can I forgive myself? I know what I did was horrible but I can’t change it now. I thought I was doing the right thing at the time, but I’m sure my boy probably suffered because of it. I loved him so much. Any suggestions on how to decrease this pain? I can’t forgive myself and I don’t feel I deserve to be happy anymore.