1. Its not totally clear to me what the goal of the app is. Is it going to help me lose weight? Help me avoid unhealthy foods? Why am I tracking? Do I get to choose why I am tracking? Tracking is a big commitment, so I would lead more with what the benefit is, to motivate me to decide to track.
2. I really love the weight watchers approach of boiling everything down to a single point count. I have been around WW long enough to see them change the meaning of the points to incentivize different behaviors. For example, raw fruits and vegetables are generally zero points, even though they clearly have calories. High sugar foods are higher in points than their calories would suggest. I find a point system much more useful than a calorie system.
Overall, if your goal is to help people lose weight, I'd suggest you look at what WW has been doing in their app, and also in how they have changed their point system over the years. I actually think WW overall (including the meetings) is an amazing system.
Interestingly, I have gotten to the point that I basically know the points of everything I eat regularly. Originally, I loved the WW app because it was so comprehensive, but now I just use a tiny notebook and pen. Its a lot faster than messing with the app.