I've lived in the area for almost 40 years
(no idea how that happened - I was only 21 yesterday!) and I can assure you that there isn't a problem re safety. Like any other London borough there is crime - but Merton has one of the lowest crime rates.
I'm quite happy to use the tube back from town to South Wimbledon, on my own, at night.
The grid of houses I live in is very family-oriented. Local primary is Pelham, which is rated 'good'. Two other primaries are 'outstanding' (Merton Park) and 'good' (Merton Abbey). The nearest secondary is a boys' school (mixed 6th form), Rutlish, which is rated 'outstanding', as is Bishop Gilpin, which is a girls' secondary. Raynes Park secondary, which is mixed, is rated 'good'.
Not sure what you mean by 'lifestyle' as that's a pretty broad term! But we have good green facilities - Abbey Rec, Morden Hall Park, John Innes Park and, obviously, Wimbledon Common. Lots of places to have coffee, a drink or a meal out. Two cinemas - Odeon multiplex and Curzon.
Wimbledon Theatre is the largest theatre outside of Central London and often has some great shows. The pantomime at Christmas is especially good!
Transport links are very good - 2 different tube lines, mainline and also the tram, which goes to Croydon (and beyond) - makes it very easy to get to Gatwick airport.