Wolf,
1. The ratzon Hashem would be that Bnai Yisrael should wipe out his nation. There’s just no reason to think that creates an individual obligation on him.
2. If there was such an obligation on him, the Ameleiki could solve the problem through via leaving his Amaleiki community and intermarrying, without resorting to suicide, which would be problematic.
Coffee Addict,
Generally we don’t assume conversion is the ratzon Hashem for non-Jews.