Hi, never cooked rabbit stir fry myself. But based on my experience of Rabbit, i would say it it important to cut it thinly and cook it hot and quickly, to avoid it going tough. Dont let it steam or it will rubberise. So cook the rabbit first, then if neccessary take it out the pan, cook everything else , then reheat the rabit in the mix. As for sauce, throw in a bit of soy sauce, honey, maybe a littel white wine vinegar or sherry vinegar. Sounds nice...
HTH
Matt