Is there any advantage to static over dynamic IP addressing?
Yes. If you're running servers from your site, you'll need (for all practical purposes) a static IP. Even if you're not, dynamic IPs can be a pain when dealing with long-term TCP sessions, like a telnet or ssh session, since if your IP address changes, you lose your session. How often it would change is an important point, too. It might change every five minutes or it might change once a week or less.
Number of IPs... What is the difference between having one or multiple
This has more to do with running servers from your site. If you want to have multiple servers accessible, it's easier, sorta, if you have multiple IP addresses, though it's not a requirement except in certain cases. Also, multiple IP addresses would make it easier to have a DMZ, which is a separate network that's more open to the internet than your regular network used for, usually, servers that need more unfettered access.
Do I need PAT and NAT?
If you have more computers that you want to access the internet than you have IP addresses, then you need NAT. You can do it yourself if your ISP is offering to do it for a cost. NAT also increases security a bit, as it implies having a firewall, too, though not necessarily a very complete one. (I haven't heard the term "PAT" in ages, but it's essentially the same thing.)
What would be an ideal connection speed? I think the 1MB package would be insufficient.
This obviously depends on how much bandwidth you need. ADSL starts at around 512kbps and goes up to about 8Mbps. T1 lines, formerly the default commerical non-dialup access ran at 1.522Mbps. Honestly, this is something that's not really answerable. You need to consider how much traffic will be being passed at once. How many computers do you have? Is it going to be all web traffic or are people going to be downloading CD images? Make sure you know both the incoming and outgoing bandwidth. If you plan to have no servers, then outgoing bandwidth isn't important, but if you do, you wouldn't want to get an 8Mbps line and then be disappointed to discover it's only 512kbps outgoing.
You might also find out if your ISP is going to provide open access to everything or if they're blocking ports or forcing you through a transparent web proxy or anything else obnoxious like that.
Also, you might want to see if they have upgrade options. For example, you might be able to get a line that's reprovisionable on the fly, so that if it turns out, for example, that the 1Mbps line you chose isn't fast enough they can just make it bigger without having to redo everything and cause a lot of downtime.