Re two neutron stars colliding. Neutron stars merging create either a black hole or a Gamma Ray Burst. During a GRB, which will last for a fraction of a second, more energy is released than our sun will generate in its lifetime. There is some evidence that GRBs have triggered at least one mass extinction in Earth's past. The energy mostly goes out in a narrow beam like a lighthouse and that gamma ray beam can pretty much sterilize a planet at a distance of 10,000 lightyears.
Dr. Larson says, " We already insert human protein into bananas to grow edible vaccines against Hepatitis B." No; although human proteins could be used in making a vaccine against humans. Instead. Isolate the gene sequence for a Hep B surface protein; insert that sequence into banana chromosomes and the banana fruit will contain the Hep B surface protein. Eating that banana will spur your immune system to make anti-Hep B antibodies. At the time this episode was made, edible vaccines was a hot new idea. By 2020 it hasn't really worked out yet.
Nigel suggests Lucas might have acquired immunity to the alien infection; "like when people take small doses of arsenic". The small doses process, mithridatism, has been practiced for at least a couple thousand years. In the cases of some plant toxins and snake venoms it does work. In cases of inorganic toxins, like lead or mercury or arsenic, it does not work.