Make sure you are driving your glutes through at lockout, but otherwise you’re absolutely fine. Feel free to add some more weight, it looked easy!
Don’t stress about deadlift form at a powerlifting meet - stay tight and keep your lower back safe, but otherwise just go for it. Deadlifts don’t require the same intricacies of technique as the squat, and maximal lifts usually look best when lifted aggressively without too much conscious thought. Analysis can limit you if you’re already at a reasonable level technique-wise.
EDIT: And yes, beltless is definitely legal if you can’t figure it out in time, but if you train with the belt you should be able to get used to it (especially if you’ve ordered a narrower deadlift belt). Good luck!