Re: Angry Cat..could use some help
I think you are doing the right thing already. Let them work it out themselves, but keep the little one safe. I have a cat who does not get along with other cats, and he is quite mean to them as well. I tried twice to bring a new kitten in, but both times I had to give them away to other good homes.
Some friends of mine have four cats: two Siamese, one little tortoise shell or calico, and one Maine Coon. Each time a new cat is introduced they go through a process of re-acclimation. They do end up working it out, eventually, although not without a few hissy-fits.
Last time I cat-sat, they had even worked out their own dinner routine: the Siamese Divas first while the little one waits, then the little one while the Maine Coon hangs out until everyone else has cleared the kitchen, then whatever is left is his.
It may take time, and if the older cat really is a danger to the younger one (as mine was), you might not be able to have two. I do think that your older one is still young enough to get used to another cat, so I wouldn't give up yet.
Good Luck, and keep us posted!