This doesn't sound so bad. If the older cat completely hated/feared the kitten, he would leave or charge/swat when the kitten was merely in the room, never mind 3 feet. I think or at least hope your getting close-ish to the "fine when the kitten isn't actively bothering the older cat" stage. Getting to toleration (or closeish) can be a long slow road, but it sounds like you've taken some steps. I know you dont want to see your older cat stressed, but stressed-only-when-actively-being-bothered isn't so bad, if your there or getting close. Its a normal stopping post on the road.
I guess I'd say this. Its clear its not going to be quick. These things often take quite a while. If your not at ok when not being bothered, it may take a while to get there, and the ok when not being bothered stage can really really linger. Usually one can get at least 95% of the way to full toleration, but issues can persist when the younger cat bothers the older cat. Usually that diminishes some, and the whole thing gradually becomes more bearable, but it doesn't necessarily totally go away. So I think its time for a deap think on your part -- can you adjust your perspective a bit, or is this just going to be a nagging burr that is going to keep your anxiety at a boil and slowly drive you crazy? Be honest with yourself and your partner. I think you can do it, but if you can't, now is the best time to make that decision and rehome the kitten.
I guess I'd say this. Its clear its not going to be quick. These things often take quite a while. If your not at ok when not being bothered, it may take a while to get there, and the ok when not being bothered stage can really really linger. Usually one can get at least 95% of the way to full toleration, but issues can persist when the younger cat bothers the older cat. Usually that diminishes some, and the whole thing gradually becomes more bearable, but it doesn't necessarily totally go away. So I think its time for a deap think on your part -- can you adjust your perspective a bit, or is this just going to be a nagging burr that is going to keep your anxiety at a boil and slowly drive you crazy? Be honest with yourself and your partner. I think you can do it, but if you can't, now is the best time to make that decision and rehome the kitten.