some of this is obviously impaired digestion. but you can get around a fair amount of issues by using wisdom from the ages.
grains - soak them for 24 hours, grind and ferment them. even some people with gluten sensitivity can handle sourdough bread since it is prepared in a traditional manner.
legumes- soak for 24 hours and discard soaking liquid. cook for a very long time in a pressure cooker until they are butter soft.
veggies- same. cook for a very long time in pot or pressure cooker until they are completely broken down.
fruits- stay with only sweet ripe fruit. eat fruit 4 hours away from all other food. you can also cook fruits to make them more digestible. stewed fruits are very good for people with impaired digestion. fried bananas or ripe plantains in ghee or butter is a good dessert. other good ones are stewed apples, berries. high enzyme fruits like pineapple or papaya can be better than enzyme pills. if you are sensitive to the fiber then juice pineapples.
(just my opinion as i know a lot of people here are doing nutritional balancing... but over long periods of time if you don't feed your body enough carbohydrate you can get very depressed and weak. some people are able to burn protein or fat as fuel and they are better able to go without sugars in their diet)
if you aren't eating rice and you see 'rice' in your stool these are parasites. well cooked basmati rice should be extremely easy to digest. undercooked brown or wild rice is hard to digest because of the husk. in ayurveda basmati rice is recommended for all types during weakness as it is easily assimilated.
marinating meat in yogurt tenderizes it due to the lactic acid. you can also marinate in vinegar (acetic acid) to help break down the proteins.
bone marrow or bone broth are both excellent for vitiated vata.
bone marrow specifically is mentioned in the vedas as a remedy for exhaustion.