Yeah I was going to mention the first person issue as well. First person can work, but it has to be more immediate to engage the reader. Instead, it's coming off like a guy telling you about his day last week. And since it's in first person, you could inject even more personality into his narration.
This paragraph for example
After only a step or two, I felt a sharp pressure in my neck, and all of the force behind my grip evaporated. My surroundings spun around me, the colors blurring together. Before I knew it, I was on the floor, immobilized. If I could have laughed, I would have. Damn near 20 years of front-line fighting, but I'd meet my end here, on the floor of a casino.
would feel more immediate this way
Two steps later, a sharp pressure pinched my neck and took all the strength in my grip. The world spun, the colors of everything blending together in a garish neon soup. The floor hit me hard. If I could have laughed, I would have. But I couldn't move a muscle. Damn near 20 years of front-line fighting, not even tested today. I would die here, on the floor of a godforsaken casino.
The key is to cut down on filter words/phrases, ones like "I feel", "I sensed", "I heard". Instead, just describe the sense outright. Since it's in first person anyway, you don't need to include so many "I"s. Like instead of "Outside the window, I heard a symphony of crickets" it would be better as "A symphony of crickets came from beyond the window."