So you buy a nice two shelf bookcase but it’s wobbly and you know it won’t hold much. I’ve recently gotten one and my solution was to put L-brackets on it. After installing about 8 of these brackets at the cojoining parts of the shelving, it is now completely stable and ready for use.
Lettuce is hard admittedly. Personally I don’t eat it. It’s mostly water, not very nutritious, and also a pretty good vector for pesticides given the edible surface area.
Spinach should keep for 2 or 3 days. Do as they did before refrigeration: put it in a dark, dry, cool (low) place. Shop regularly in small quantities - people alone in apartments tend to be in big cities where this is possible.