I was in a similar situation and made a very similar post a few years ago you might find the discussion relevant:

https://www.reddit.com/r/fulbright/comments/lkm2fq/career_impact_of_fulbright_in_late_20s/

Anyways I ended up deciding to go for a research grant. I think that is a solid option for you to consider if you decide to turn down the Fulbright. An ETA fulbright is still a great opportunity but I see where you are coming from. Is the language of the country you are moving to relevant to your nonprofit work? That could make it worth the career pause. I think in your shoes I would also just think over what will really matter in the long run, like in 40 years will you be happy that you got 1 year ahead in your career or that you spent this year abroad? On the other hand, are you set on living in your host country long term, or could you be content with 2–3 months backpacking in between jobs? Ultimately no bad choices here, doing the Fulbright or turning it down are both reasonable in your situation and no matter what you do things will likely work out!