Excellent take on a Null subclass. The use of sonic damage, ranged punches, and reverberating abilities all tie together quite nicely. Throwing the null field at enemies is very clever.
Similarly to others, I have some concerns about Repeat. It's a very cool and thematic ability! But the extended nature of it looks very easy to lose track of and forget in a fight with lots of moving pieces. Might need a rework in a way that's still satisfying without needing the extra bookkeeping. Noticed a handful of punctuation/spacing errors as well. Nothing that's detracting from the score, just a note for when you do another editing pass.
Everything considered, excellent submission. I'll toss this to the Null fan at my table to see what they think of it.