2 modes of radioactive decay for hydrogen-5?
Sorry, you haven't.  I don't know where your information is from but I think there is an error in your decay chain.  For the 0.9% of $\ce{^8_2He}$ decays that proceed via spontaneous fission your equation should look more like this:
$$\ce{^8_2He -&gt;[fission] ~^3_1T + ^5_1He + \beta ^{-}}$$
$$\ce{ ^5_1He  -&gt;[neutron~emission]  n + ^4_2He} $$