You can send more, but it's not recommended, as if you send more boxes per day -- including the daily boxes -- you'll get a good week review, which can reward you with more money. Like, 500+. However, if you need more ways of making money, you can sell trash, sell food if you have more than enough. There's tons of ways to get early bits of money, and I've covered a lot of it if you wanna visit my tips thread sometime. Lots of tips that might help you!
As for crafting, if you have enough materials on the bench to craft scrap, or a recipe, you'll see a new option pop up on your radial menu.