4m will be a nice size for you are you are quite big, just make sure that you start with it in no more than 15knots of wind. Foil kites fly in not much at all so you will be able to pricatice in anything from about 5 knots. Learn to fly the kite very well before attempting the board, make sure you can fly it with out even looking at it.
any entry level board from a good manufacturer will be fine. scrub, kheo, mbs, RKB make good boards at reasonable prices
Definitely not too old, most of the people that do kite sports are middle aged
kitesurfing camber