The only random idea I had was that, maybe, MC was never a mutant in his previous life and he actually got trained growing up, and ML didn't actually erase memories of his family, he erased his memories of life in the Center instead. And these dreams are just a bit of that returning to him.
It would kind of explain why MC improved so quickly at shooting, and why he felt familiar with the goggles, and a few other tidbits. But it doesn't match some other stuff so it's probably just a crazy idea.

Gosh I really want to know what happened in MCs past life, I think it's related to the ML because of the fact that he keeps appearing in MCs dreams, it's like a preparation for something and I'm afraid by the end of the story the ML will die huhu. ML is definitely in between a black and beige flag, he might have his green flag moments but it doesn't compare what MC had gone through both in his past and current life ಠಗಠ