Hi
The key is a stable internet connection. The problem with poor ADSL via phone line internet speed areas is the line quality can vary a lot. This affects the speed the line can handle, and sometimes can drop the connection if the line quality is very bad. A big factor is also the line distance from your house to the serving telephone exchange.
In the UK the superfast broadband via a phone line is called Fibre to the Cabinet (FTTC). A high speed fibre optic cable services the local cabinet on the street corner where your phone line is connected to. From the cabinet to your house is a short run of copper (your existing phone line) which is much more stable and can handle high speeds because of the short distance from the cabinet to your house.
The other option is whether your new area has cable TV. This is fibre optic direct to your house and the cable TV provider usually offers a broadband service as well.
Your questions:
1. I think 2mb/s is the minimum, but the important thing is must be stable and not drop. Also, at 2mb/s no one else in the house should be streaming / downloading etc.
2. Yes. I had a 6mb/s ADSL service which varied in speed a lot, and dropped from time to time. I changed to the ISP's superfast broadband via FTTC. It has been rock solid since changing. I now get a constant 57mb/s download and 12mb/s upload. The street cabinet is 500 metres away, and the telephone exchange is 6km away.
3. Yes, especially if you are monitoring lots of markets, or have a big list of bets. If you are getting a new PC anyway, the spec will be much higher than the minimum spec required for MFP. A ball-park suggested minimum spec: 2.0Ghz processor, 4GB RAM, 500GB Hard Drive.