Your snake will not become cage-aggressive if you feed in-cage. Almost every single person on this site can attest to that. Just so long as your hands don't smell like rodents when you reach in, the snake will never mistake you for food.
In addition to the other suggestions made, I would also really recommend getting a digital thermometer and hydrometer ASAP. It's extremely important you know exactly what your temps and humidity are at all times. Inproper husbandry can oftentimes cause a reluctance to feed. The dial-type gauges are often inaccurate and have a limited lifespan.