...and I still have Simba. >.>
Ended up switching back to regular store food, and serving dry food, as could not afford the vet stuff at one point which ran out of too quickly. Yet, once back on dry food, while alternating with wet food once a day, Simba got noticeably better. I am sure still has whatever problem, but his body appears to have adapted. After few weeks, went back to regular full meals, wet food every day or so while having a full bowl of dry food once a day or so. In turn, stops waking me up throughout the night, at least until around the time i usually wake up for work. He even started shedding a lot again, requiring to get a new brush for him. Once get a proper self-contained kitty litter box and resolve the smell, both our quality of life should normalize. Meanwhile, no news about his sister. :/
Now the furball is looking at me expectingly to give him more food.