I finally decided to read the adoption papers. Turns out he's not 2.5 years like the paper on his cage said and like they told me. He's 3yrs 10months. Not that this matters at all. He also was treated for ear mites, had two doses of Convenia and two doses of Penicillin. I do vaguely remember them saying he had a cold or URI when he came in and was in quarantine for a few weeks. If he was in this bad of shape that may account for why he's so skinny.
I think I made a breakthrough. Today him and Onsa were at the food bowl, she growled and then walked away. This is the first time she actually walked away. Samai is out of hiding and on my lap. Onsa slept with me again, and Kumal has been sleeping on my elderly mother's head. They are still cautious and curious about him, but they no longer run and hide or want to kill him.
Just spoke with the shelter and they said that him and another cat were alone for some time when the owner died. He was in such bad shape that this is an improvement.
He has put on a little weight...like ounces. This is going to be a long haul, but I expected that.
Him and Onsa were about two feet apart laying on my bed, with no hissing. All is going well.
Sorry I'm late to the party. I must have missed your thread but would like to congratulate you on the adoption of Kumal. He is an extremely handsome black beauty. So thankful the cats are working things out and getting along better. Kumal has found his forever home. Best of luck!