The 401 sounds good. I'd refrain from putting in more than 60 hours per week in something work-related. Focus on the studies as they might remain your primary and most reliable source of income and don't damage them with fatigue and limiting your attention span.
Regarding Acorns - any investment tool that limits my options is a bad one. Thinkorswim is indeed a great way to get to know trading and investing and forming your own knowledge and opinions. I think there's better value there than that of some app looking to make a buck from your buck. It remains to be seen how they perform over the long-term with their portfolio types.