Regardless of the actual punishment for a Gentile unintentional manslayer, he can only obtain full atonement through being killed according to Likkutei Sihot vol. 24, p. 107.
Also, Gentiles do not have Cities of Refuge for an unintentional manslayer to run to outside the Land of Israel. But if a Ger Toshav kills another Ger Toshav by mistake, he may run to one of the Cities of Refuge that will be in the Land of Israel.
There is an ideological overlap between Chabad and Kahanism. The Rebbe supported Rav Kahane. Chabad Rabbis like Weiner and Schulman teach that the Arabs have to be expelled from Israel. Have you tried pointing out this overlap to Chabad leaders? Maybe they would be willing to support the Hilltop Youth financially?