There are several gain stages in most audio paths: the wireless mic output, gain on your mixer, channel volume on your mixer and then master volume on your mixer. Once the signal hits the ATEM you have another volume there as well. You can bring up the level until the loudest sounds hit yellow on the led meter on CamSlicer. The trick is to increase without hitting distortion.
Keep in mind that national ads are professionally produced – from a video and audio perspective. They run a boatload of compression and other audio processing to make them “sound” louder than the surrounding video. It’ll be a challenge to equal commercial production audio without adding some outboard gear. I’ve had luck in the past with combination compressor / limiters.
Recommended: Behringer Composer Pro-XL MDX2600 Compressor with De-esser – approx. price: $200