What is the ideal fridge temperature
The USDA says refrigeration temperature should be 40°F (4.4°C) or below. If food is in there at a higher temperature (such as the 43-45°F the question mentions), for longer than 2 hours, and they're saying the food isn't safe.

Keep in mind that when too cold, after a while parts of things freeze, which can damage items, or severely diminish their pleasant taste. This especially goes for produce such as lettuce or even tomatoes. If you want to store leftovers longer, consider freezing them.

Edit: corrected to 40°F or below