Abalone pearls need no treatment. They are organic gems. They can dry out in extreme conditions like lying in the sun for years. They need the same care as abalone shells, which is to say, not very much.
That is still a large pearl! Huge! You would probably just get a low, low wholesale price for it, if you sell to a reseller. If you put up more angles of it in photos, one of the abalone buyers here might see it.
Actually it is so large, not many resellers would even consider buying it because it is hard to set in jewelry- except maybe a belt buckle. It would be quite difficult to resell at current abalone prices.
Maybe you should make it into a belt buckle and enjoy wearing it yourself. This is just my 2c, wait for other responses. I personally am abalone crazy, but the prices are so high in general, sales really suck for abalone pearls. I have literally seen the same ones for sale for years on more than one site- esp. the bigger Pearls. Some sell slowly, very,very slowly, even by the top names in abalone pearls. Small to medium size gem grade abalone pearls seem to be the only ones that sell at all.
Abalone owners have a very inflated idea of what their pearls are worth, but in the real world, they will never sell for anything near their perceived value.