Dwayne stopped just inside the entrance to the ballroom and adjusted his jacket while he looked around. He couldn’t remember the last time he had worn a tuxedo. He was much more comfortable in jeans and a t-shirt. All the people here wore fancy get-ups, though. All the men were in tuxedos, and the women wore dresses that sparkled. In fact, the women seemed to be having a competition for who could sparkle the most.
Dwayne didn’t know where to go. He wanted to wait for Leslie out of everybody’s way. His heart skipped a beat. He hadn’t seen Leslie in ten years, not since they graduated high school. He had thought about her often during that time. On a whim, he’d recently signed up for an online program that reunited people with others in their graduating class.
You've firmly set deep penetration 3PL; don't break it and you're fine. Here's what I think you need for 3PL deep:
* An initial entry into the MC's thoughts. It can be "he thought," or it can be a thought in which it's obvious who thought it, as in
"It looks beautiful," Joe said, looking at the ring. And expensive. It would be two month's salary. Did she think he was made of money?
* Start making thoughts without the "he thought" tag.
* Avoid putting Joe's thoughts in the same paragraph as Mary's dialogue; it's a cue that it's Mary's thoughts, so it becomes confusing.
* ...and, of course, no actual POV violations, that is, showing things that aren't Joe's thoughts or perceptions.
It seems to me you're a natural at this. Or else you've already worked hard ot look like one!
Rewrite like this: He was way more comfortable in jeans and a t-shirt, but all the people here wore fancy get-ups
"In fact, the women seemed to be having a competition for who could sparkle the most."
Comment: It sounds kind of weird. I would take that sentence out and replace it with something else.
Other than that it is very good!