This was an unfortunate and toxic experience for you as you invested yourself in the world you created. Your brother's lack of regard for your feelings may extend beyond the gaming table. Hopefully your relationship with him can be improved but for that you need his support and willing participation.
It's not surprising that the world you developed now provides triggers for bad memories. Rather than walking away from your creation, I humbly suggest starting small-- maybe a couple one evening episodes with a trusted player or two so you can start rebuilding the sense of enjoyment the setting once provided with some positive experiences.
Best wishes in gaming and with your brother, hopefully there are better times ahead.