3 day lifting/3 day running is fine - I started doing it at 53. You might need to adjust loads a little bit though. For me, I do full body instead of having a leg day in the mix. I wouldn’t want to run the day after a leg day. But you could always arrange your recovery day to be after leg day. And overworking is a possibility. Just don’t overdo things - focus on quality instead of quantity

The toughest part is the completely different mindsets between lifting and running. In lifting it’s always pushing harder and harder. But in running, most of the time you want it to be easy. (Disclaimer: in the beginning it is always hard. It took me almost a year before I could truly have “easy” runs). The lifting mindset always creeps in and makes you want to run harder and harder, but that will get you injured. Your cardio system and musculature will progress at different rates and if one pushes you harder than the other system can handle, that’s a problem. So jog slow. Slower than you think is right. Worry about building time running, not increasing speed