I don't live there, but I used to play squash with a friend there.
1. The gym is of a decent size for a residential gym. Good range of equipment.
2. There's a Wellcome supermarket nearby, but not a very good one. A decent Park n' Shop on Smithfield Road, opposite McDonalds. There's also a government operated food market on Smithfield Road, but geared towards locals. The Belchers (a large residential complex) is about 15 minutes' walk away and has a much better supermarket.
3. No tennis courts nearby except, again, at the Belchers.
4. Can't say, but there are plenty of transport options.
5. No. Closest station is Sheung Wan, which would take up to half an hour on foot. They are extending the subway line to Kennedy Town, but it's going to be years before there's a station.