What to do?

Is he competent? If so, then, I'd let him decide what he wants to eat. How has hospice responded?

I think someone on hospice should be allowed to eat whatever they want. You don't mention that he has dementia, so I assume he is competent to judge when something is too hard to chew or swallow. If certain foods make his chronic kidney disease bother him more, he can decide whether eating those foods is worth it. Similarly with the CHF. If salty foods make him retain fluid and the buildup is bothersome, maybe he will choose to avoid salt for a few days.

I think the goal should be to avoid discomfort now, and not to worry about long-term complications. And as long as he understands the potential short-term risks, he should be the one to make eating decisions.

I'm all for letting end stage patients do whatever they want. But, if it causes MORE physical problems, then it's counterproductive.
For example, if your dad is craving potato chips, which are loaded with salt, it could impact the CHF. If he craves meat, that can impact the kidneys and sweets mess up the diabetes. Wow, there's not much left but lettuce!
Maybe he can have small amounts of the prohibited foods like no sugar sweets, low salt potato chips, soy hot dogs, etc.

You can't deny everything, especially in the last stages of life, but if you can juggle the treats, it may work.

Contact his doc and ask what his recommendations are for giving forbidden favorite foods.

My husband had diabetes, CHF, and arterial sclerosis. He had been following a heart-healthy diet all the years we were married. When he was diagnosed with dementia both his neurologist and his PCP (a geriatrician) said he should eat whatever he wanted. Wow! That was a change. And that is what we did for 10 years. When he went on hospice I took their advice and continued to offer food but did not try to coax him to eat.

With your dad on hospice, Nikki, your dad may not want to eat. But if he wants to eat potato chips, I say let him! Whether he eats kale or twinkies at this point is not going to make a long-term difference. If certain foods increase his discomfort he will probably not want to eat them, without you establishing restrictions.

My mom was stage 5 ESRD, COPD, twice cancer survivor, congestive heart failure, topped off with dialysis delirium. Mom decided she wasn't going back to dialysis and I couldn't persuade her to go. Took a lot of abuse from the dialysis center for *her* decision, so much so that when the dialysis center social worker selected not to call me back for three days, I called my mother's physician to call hospice as I didn't feel the dialysis center was happy with her wishes. Hospice came in and said she could eat what she liked. At the end, does it really matter if you are eating something forbidden?? Not knowing where she was when it comes to passing, we tried to accommodate everything mom wanted. The only thing I didn't manage was the Pepsi she asked for. I was unable to leave the house for about two weeks and I hadn't heard her say Pepsi in roughly 30 years.....the only place she would buy them in was her home state of North Carolina. She said they tasted different when she moved to Baltimore.
She lived three weeks after stopping dialysis. I did what I could to help her enjoy her last days.

@suec1957 it's so hard and confusing feeding him because certain foods is good for heart but bad on kidney and so on...don't know how long he'll live so I don't want to give him nasty tasteless bland food but in the other hand I don't want him dead soon because of "good" food

Dad doesn't know the severity of his illness nor that he's in hospice. He thought he's staying with me to rest and get better. He just complains he's tired no major pain. And when he does have pain I don't really know if it's from the food he ate or not. It's hard to keep track on him.

My concern is, as others have mentioned,-that what he eats may affect hs health so seriously that he has an episode related to his CHF, renal disease or diabetes. Other than that eating what he likes makes sense. To me that would mean managing his diet to the extent of avoiding episodes as much as you can, but within that, and probably sometimes outside of that, letting him have the foods he wants. It would be all about keeping him as comfortable as possible.