You probably need an attorney qualified in nonprofit law.
One strategy might be to word your documents to refer to surrogate identifiers for the population you want to help. E.g. say that your group is set up to help “Non-native English speakers in South Texas”, when you and everyone else know that means “help Hispanic people”. Sure, there’s an off chance you might end up being “forced” to occasionally help a lost Quebecois tourist or a Yiddish speaking Hasidic Jew from NYC stopping on their way to LA, but that’s the cost of doing business, but most people will implicitly understand what your group is about and leave you alone unless they are your real target market.
While small nonprofits organized by ordinary people for local purposes (little leagues, community groups) can be casual about the details, an NPO that intends to take federal money is walking a tightrope over broken class and razor blades. I would not, under any circumstances, attempt to organize, qualify or run one without a competent attorney in the mix.
A non-profit does not have to provide services to everyone. That’s true even of a 501c3 nonprofit.
However, you’d want an attorney or other expert in non-profit law and government grants to help you parse the details. If the services are too specific in nature, you might wind up with some kind of fraternal or trade association. They’re still non-profits, but not charitable, and perhaps not eligible for the grants you’re thinking of.
Federal grants often require additional level of oversight and accountability than are required of a non-profit in general, so you need to keep multiple sets of standards in mind.
People do not get non-profit status, organizations do.
I’ve dealt with hundreds of federal grants in my day, and dozens of start-up non-profits that really have no idea what they’re doing, what a non-profit is, etc. I don’t mean to sound caustic, but there is plenty in your post that reminds me of those organizations. Extremely well-intentioned, but very much ill-equipped to deal with the hassles of a federal grant.
If you’d like a little non-legal advice, feel free to PM me with further details.