Components of fitness for a 40 year old

What is fitness? Many things to many people I suppose, but for me right now here are the components I'm thinking about.

Cardio-vascular endurance (Sorry for anyone reading this getting terminologies mixed up, but basically I'm talking about longish runs - 5km time trials are pretty good in this respect and I'm fortunate that the Pollok park, parkrun is near the house).

Aerobic endurance - turns out it's the same thing as cardio-vascular endurance, but in the gym I'll use the 4 min rowing test for this anyway, although I reckon I'm never that far from Anaerobic workouts on that bloody ergometer.

Anaerobic fitness - this is really about the ability to recover from working flat out for a short burst. I don't really intend to do anything specific about this just now as I reckon trying anything that intense given my current condition will just lead to injury. Eventually I suppose it'll be like a game of squash or 5 a sides, but I probably still won't measure it.

Strength - Well, I'm probably beyond the stage of shifting weights about the place for posing or looking to make muscular gains, but body weight exercises seem a pretty reasonable guide. I'm thinking that power to weight ratios are probably best tested with the press-ups, dips and pull-ups, especially the pull-ups, unfortunately.

Weight - I'm going to use the BMI thing as a decent guide here and I'm way overweight. Plus I've got too many pairs of trousers that are now not comfortable, so I'll be saving a fortune if I can drop a few cms round the waist.

Flexibility - I've ignored this for my entire life, but it's something that I intend to address in this new regime. But how does it get measured. I'm going to try to find a sit & reach box - maybe I'll ask the gym to provide one.