2. A portal of the type the monster comes through could indeed cause a dimensional disturbance that destroys all signals passing through.

6. I know them. Maybe the smaller monsters spring off of the big one because they are actually part of the big one that can separate. These organisms reproduce and mature deep inside of it so it gets stronger and larger as time goes on. However, it needs a lot of energy to keep this process going.

7. "Team up" is them using the monster for their own gain without the monster really aware it's being used. The story could take place when the UNT is at war with the largest Empire in the galaxy and one agent managed to infiltrate the planet and could disable vehicles. They are called the GAN Empire. At the main timeline they are not at war, at most in a cold war but are not beyond helping each other on occasion. They respect each other at least somewhat and follow rules of war so are not transparent villains like the Empire from Star Wars. During the big war between them these rules were more lax, although both of them still agreed not to use weapons of mass destruction because if they did they would destroy the galaxy and neither side is suicidal.

8. There could be a canon where the Threat is more successful due to the lucky breaks, which will be the one we will keep in canon for these arena battles. It will not be a stick in the woods planet, just not a super major planet that would easily repel the monster even with all the bad luck in the world unless they all had heart attacks. XD

We can say it's a moderate planet and close enough in UNT space to threaten other planets later on. It's only separate from the rest now due to the dimensional disturbance.

The heroes retreating would make them less heroic, now wouldn't it. XD