Slow cranking sounds like a classic battery on the way out symptom. Many auto stores will test the battery and charging system for free. They roll a cart with a load tester out to the car. Note that a battery can have good voltage, ie lights are bright and such, but still be failing. The load tester checks the voltage drop while delivering several hunderd amps of current, simulating what occurs when cranking the engine. That will call out a failing battery.

It's normal to be able to turn on the radio without the key - just push on on/off/volume knob. It's a feature, not a bug.

I have no clue on the low airflow issue...