@ZeroPucksGiven that's a difficult situation, i feel for ya.
as far as running goes. I have done a variety of beach body workouts and the first p90x really made me fit. I'd give that sorta routine as my #1, but running is fantastic for getting you in shape. I'm not talking about running at a pace you can give a lecture, you do that as process to get where you want to be.
For myself when I was actually running, now i'm too old and fat, 4 miles was the perfect distance. I'd try to keep that under 30 minutes I endevored to maintain a 7m mile pace but that was difficult for me to do for 4 miles, but running at that intensity level for 30 minutes was just the right amount of time and intensity for me. Now I threw numbers out there, but for a real runner it's not impressive, my buddy would run 10 miles at a 6m mile pace all day long. My only real point is if you work yourself up to where you can do fairly intense state for about 30 minutes you will burn a crap ton of calories and the cardio benefit is incredible.
My cardio fitness level when I was doing that 4x a week was great. In fact I feel like me doing that for a couple of decades gave me a cardio base that I still have.
I agree for getting back into it that you can't hit that level of intensity for quite awhile you have to slowly build back to it. By slowly I mean depending on where you are you might be walking for a few weeks first. Some great advice earlier in this thread about easing into it.
For longer runs I actually loved it at the time, and I am not built like a runner at all, but you get the right kind of music going and I could basically zone out and run, focus on my breathing. Very yoga/mediation like when you get into the zone. In fact I still remember when the remains of a hurricane went over pa years ago, Irene? , and it was a steady very warm rain. I ran 10 miles in that and it was a surreal experience that I still remember to this day. I have never experienced that sort of feeling from any workout I've ever done.
These days, I've toyed with getting back into running but I'd have to drop 20 lbs and really ease my way back into it or my knees will complain loudly at me. I know this because my daughter did a 5k, and I hadn't run even a step in years. So I was like I'll go run with you. I felt great doing it at a very moderate 9m mile pace i talked the whole time. Next day my knee let me know that I hadn't done anything like that in a long while, took a couple days for the inflamation to go down.