Shalom, I do not know of any source that says what is the punishment for a non Jew for wasting seed. But I do know G-d does not approve it and dislikes it very much! Therefor a non Jew must also be very carful with this sin and any type of forbidden relations. If a non Jew has already committed the sin, his Teshuvah should be by not repeating the sin anymore, having regret and remorse, educating others about the severity of the sin and living a life of truth and honesty. You are right, Non Jews are not obligated to study Torah and some subjects they are prohibited to learn (only because spiritually it can harm them) but there are many other subjects that non Jews can and even must learn in order to know how to act as Noahides and also to know what G-d is expecting from them. Since a non Jew can not correct the sin of wasting seed by learning Torah, my suggestion is to support a Jew that does learn Torah and by that the Non Jew can benefit from the Torah the Jew learnt. We have many non Jews supporting my men's Yeshivah where they learn Torah and they take part in the Torah Learning. Wishing you great success Alon Anava