For your stats I would recomend you get range to maybe 75 and hp as high as possible and at least 60 prayer
Since you dont want to melee heres what i recomend:
Take Karils Crossbow and about 3k bolt racks and wear god cloak (from treasure trails) and a god coif or robin and ranger boots, archers ring, black dhide body, barrows gloves from rfd (black dhide vampbraces if you dont have barrows gloves), ammy of fury, and i used veracs skirt for prayer bonus and some melee protection just in case but you can use black dhide chaps if you want.
Your inventory should have 6 sara brew (4), 15 super restore (4), 3 ranging potion (4), and 4 high healing pieces of food, i used tuna potatoes, these numbers can be shifted slightly to what you feel you need.
the strategy is essentially just hide on the north side of the italy rock as far south agains the rock and against the east wall as possible when the waves start in hopes of trapping everything around rock and then moving to trap anything that decided to come from the west and to kill the 90's first with mage protect on at all times after the 360s show up and drinking sara brews for healing and then a super restore dose to counteract negative effects and use ranging pots as needed after the 180s start showing up just make sure to save 1 or 2 doses of sara brew and range pots for jad
I've never gotten the cape but I've made it within 2 waves of Jad and my reason for failing was bad luck (180's spawned to west and i got hit by them and 90s when trying to trap and got to close to a 360) so i know this works
Hope this helps good luck