One reason could be that he's on a mission to find other heroes in the universe. He believes that Earth needs more allies in case of future threats. So he leaves Earth to search for powerful beings or civilizations that could potentially help protect Earth. He embarks on this journey alone, relying on his Iron Man technology and his wits to survive the perils of space travel.
The South Pole could never leave Earth. The South Pole was the southernmost point of the Earth. If they continued south, they would reach the South Pole. The South Pole and the North Pole were the two poles of the Earth, and their latitudes were both zero. If they continued south from the South Pole, they would enter the southern hemisphere instead of leaving Earth. Similarly, if one continued north from the North Pole, they would enter the northern hemisphere. Therefore, no matter if one set off from the South Pole or the North Pole, they would not be able to leave the Earth by walking along the meridians.
They would be very protective. Autobots are known for their sense of justice and protecting the weak. So, they would immediately surround the reader to shield them from any further harm. Bumblebee might be the first to approach the reader gently, trying to communicate in his beeping way to let the reader know they are safe now.
The Autobots would likely be very protective. They are heroes after all, so they would immediately sense the vulnerability of the abused reader and do whatever it takes to keep them safe from harm. They might also be gentle and patient, understanding that the reader has been through a lot.
He might leave to protect Kara and the unborn child. Maybe he discovers that there is some kind of danger following him that could put them in jeopardy, so he decides to sacrifice his time with them to keep them safe.
One common theme is friendship. Usually, the human forms a deep bond with the Autobots, like in many stories where they start as strangers but end up being like family. Another theme is adventure. They often go on quests together, either to find a new energy source or to defeat the Decepticons.
One interesting 'human autobots fanfiction' could be 'The Autobot's Human Ally'. It tells the story of a young human who stumbles upon the Autobots and forms a unique bond with them. They go on adventures together, fighting against the Decepticons.
Another might be Captain America and Optimus Prime. Captain America's strong moral compass and leadership skills would pair well with Optimus' own leadership and sense of justice. They could lead their respective teams in a united front against a common foe in the fanfiction. For example, they could be strategizing how to take on a combined force of Hydra and the Decepticons.
One interesting crossover could be a story where the Avengers and Autobots team up to fight a common enemy like Ultron who has somehow allied with the Decepticons. The Avengers' superpowers combined with the Autobots' advanced technology would make for an epic battle.