If the Plot World were a pond, Li Xu would be a drop of ink that fell into it. If the ink were to spread out and merge with the pond, it might appear to expand in volume, but it would lose its original color. Such a prospect is definitely not the right path.
The correct state is that Li Xu should be like a high-density piece of thousand-year-old profound ice, falling into this pond, completely freezing it, and thereby becoming one with it, without losing a bit of its density or a hint of its temperature.
But what is he now? At best, he's just a bit darker than the average person, his spiritual power having just barely touched the upper limit of ordinary people. In the Plot World, he's just achieved a spill-over of spiritual power, far from the state of that thousand-year-old profound ice.
The refining process from ink to profound ice is the path that Li Xu needs to walk, not the pursuit of Domain, Divine Kingdom, skills, or transcendent abilities.