Content Scraping / Data Copying — reverse engineering software

I'm in a difficult situation and trying to figure out my next steps.

reverse engineering software. I've been dealing with this for about 13 weeks now and the situation isn't improving.

This involves original creative work over the past 16 months. I do have documentation proving my ownership and timeline.

Do I have a strong case? What should my next steps be?

Honestly, a competitor reverse-engineered our desktop application and built a compatible clone that reads our proprietary file format. They're marketing it as "compatible with [our product]." We have a EULA that prohibits reverse engineering. What are our options?