Let me try to answer your questions:
1. Ask for it anyway. You are moving to a new address and some will transfer the adsl to a new phone for free/a reasonable price. If not, you will have to start again
2. Yes. Very rarely they are locked to a single ISP, but you can try
3. If you get an adsl wireless modem router for your bb connection, you do not even need that. If you are going to use a USB modem, that is all you need in hardware. You will need a firewall, antivirus and anti-spyware software for your partner's laptop.
4. No. You are setting up 2 pcs that share an internet connection. Turning that into a network is trivial - just changing a couple of software settings
5. Essentially, yes. You will have to install the printer software on his laptop. However, if you set up the network, he can print across the wireless connection to the printer attached to your pc. This assumes your pc is running.