uh

due to being cut in his midsection a lot of his gut was either damaged or rearranged entirely. Zabrak are carnivores with probably shorter digestive tracts so its not as much of a problem as it is for humans who need to have much or all of their large intestine removed, but nonetheless he would probably have an ostomy bag + stoma of sorts or scifi equivalent (however this might change between various leg iterations). Its hard to tell how this condition would affect him outside of how it impacts people in real life who have this condition (crohn's disease or severe forms of ibd), but eating primarily meat might make it a bit easier on him? Something I might research more idk... Going along with that he would need an artificial blood dialysis device because he doesn't have kidneys anymore. All of this leads to him most likely having bad nausea/pain or feeling sick when his diet or meal timing changes.

Because of all this organ shifting, there might be more pressure on his diaphragm leading to less lung capacity, however being a zabrak with two hearts counteracts this and he's probably on par with any athletic human.

Due to eating like...garbage and probably fucked up things for many years, his liver had to work overtime and as a result he has some signs of liver disease, though it should be under control post spider legs and rejoining civilization. Likewise his stomach is also probably permanently smaller due to a long period of malnutrition.

Inside his prosthetic waist area would need a Thick layer of cushioning because the waist is not a real load bearing area of the body. Like any other prosthetic, there should be some way for him to detach part of his midsection so he can bathe properly and avoid any skin irritation (but it probably happens anyway if he doesn't do any self care in that area for a while)

His spine was severed so he has some pretty hardcore back pain as well as metal/robotic supports lining the inside and outside of his spine. Using a cane would help as it could alleviate pressure against his midsection and damaged spine, putting that weight towards the ground instead (this is also why i love maul with a cane in rebels).

There's probably ways to regain levels of sensation and tactile feedback through his legs (luke had a very responsive and seemingly sensitive prosthetic hand) plus nightsister magic probably gives some ethereal force connection to increase sensation and feedback. This might also be how maul can resist his body rejecting all the parts that are both embedded in him and against his body 24/7, its star wars there's magic sometimes. His legs are probably rechargable overnight and with some long term background battery (imagine uranium batteries like rovers and other space instruments have) to fill in time between charges. Maybe they can also convert food into electricity i dont know how star wars works.