Yes, your response "We are here for it. I’m glad I made you smile" is grammatically correct. The phrase "We are here for it" generally means that you support or appreciate something, in this case, your friend's enjoyment of your videos.
You can rephrase it in a few ways, such as:
1. "I'm so happy to hear that! Your laughter means a lot to me."
2. "I'm thrilled that my videos bring you joy! Keep smiling!"
3. "I love that! It's great to know