I don’t think that you need to prove your work hours any more than a student officer in school government would. They should take you at your word.
Can’t wait to see how this all turns out for you!
Working to help support your family cannot possibly be held against you as it relates to involvement in clubs or charitable organizations etc.
What you are doing is such a testament to your character and that is something that elite schools really value. Your being a first generation college student, coming from a low income household and having the grades you have, and hopefully doing very well on your standardized tests will have you stand out in such a positive way, you should have many great school alternatives to choose from.
Please do not hesitate to inquire/ask myself and others here in any area of this process that you would like assistance with! Everyone here has such admiration and respect for kids like yourself I/they will do everything they can to help.
Seriously. Apply now:
http://www.chicagoscholars.org/apply
You don’t need to document hours. Most applications have space for you to record paid work. Doing skilled work like masonry at your age is amazing. Just listing it is enough. You may want to incorporate it into one of your essays. Try to be upbeat and don’t make it sound too much like a sob story since admissions officers can be tired or wary of those sorts of essays. So instead of “Whoa is me. I had to work while others my age got to have fun and do extracurriculars.” have it be more on the line of “I met some amazing people with some great stories while doing these jobs, they gave me inspiration, etc.”
Also, start building a relationship with your guidance counselor and teachers now. Explain to them what you want to do for college. They will likely include this bit of your background - working long hours - in their recommendation letters, which can only help you. I did not see the letters my daughter’s counselor and teachers wrote, but I know they like and respect her, and I think that they must have written some excellent letters because she got into some schools that her grades would indicate that she would not. She goes to an urban high school with a low graduation rate (60%), which I also thought might hurt her, but the guidance counselors include a lot of school background as “setting the stage” in their letters.
Finally, agree with looking into Chicago Scholars if it works for you. It sounds like you are exactly the sort of student they are looking for.