No question, Sevenoaks is the easiest commute, as it's closest to London Bridge and has the most trains per hour. Lots of Americans there. Pricey though, if that's an issue.
My wife and I lived in Tunbridge Wells for a while. About as far away as you'd want to be with a reasonable commute (depending on your husband's tolerance), though having said that, we're 20 minutes further down the Hastings line. Can only speak to the area where we lived, near the Pantiles, which was extremely convenient to the station with a 5 minute walk, and a couple of supermarkets close at hand. Village-y sort of feel, more pleasant than Sevenoaks in my opinion. Unfortunately it's still possible to get neighbours from hell, no matter how nice the area...
Of all the areas around London, this is our favourite. Train line's OK as these things go (if stupidly expensive, as everywhere); great scenery; we like living between the city and the sea, for easy-ish visits to either on the weekend.