Ad Astra – How Realistic Was It?

Mars to Neptune in 68 days. Communication between the two planets via "laser" almost instantly. The necessity of being near Neptune to study exoplanets. An anti-matter machine that can destroy Earth from Neptune, but somehow we can't destroy it from Earth.

Then there are potentially possible, but implausible occurrences: surviving a huge cliff fall on the moon, instantaneous monkey implosions (explosions?), inability to track a spacecraft with its communications off, mutiny on a well organized space mission.

I'm happy to give artistic license liberally (and any Moon shoot-out scene is admittedly fun), but this one seemed to have a bit too many science holes. Am I wrong, are there plausible explanations or is this just sloppy sci-fi?