Cocoa butter and soy wax will probably be the best palm-free, vegan options for you then.
Cocoa butter at 10-15% will add significant hardness and longevity. I've never used soy wax, but there are some great threads here about using that.
I would also say that the
soap calculator doesn't always give the full picture. The people using my handcrafted soap (including me, hahah) care the most about the scent, whether it agrees with their skin, and if it bubbles the way they like. How long it lasts is usually quite far down the list after those top three concerns.
I make exactly one high-OO soap, and cure it about three months. While the bars don't last quite as long as my more balanced blends, no one complains that it melts away fast. The soap agrees with their skin, bubbles really well, and smells great - so they are happy.
All that to say, I'd encourage you to make a small batch of your recipe, as-is or with some cocoa butter and soy wax added. Give it a nice cure, and see what you and your testers think.