Having a switch in between them is pointless since any computers connected to that switch won’t have Internet access. They wouldn’t have access to computers behind the router either since the router’s firewall blocks access. The whole point of the router is to make Internet access available by sharing the single (and apparently static in your case) public IP. That public IP is assigned to the router's WAN IP. Now all the computers BEHIND the router are on the same network (typically 192.168.1.x) and share the Internet.
So something just doesn't make sense here. If the only things attached to the switch were the modem and router, it would work, but it just wouldn't serve any purpose.
When configuring DSL, you can specify the WAN connection type as either static IP, or PPPoE if it requires a username/password.
However, I guess I could get rid of the switch all together (I sort of wanted to keep it, more ethernet ports, but not a big deal).
I wasn't suggesting you can't or shouldn't use the switch. I agree, the switch would be useful for adding more ports. My argument was WHERE you were placing that switch, on the WAN side of the router. You certainly can do that, but I just don't understand why you wouldn't put the switch BEHIND the router to add those ports to its switch and a) place all computers and devices on the same network (the one behind the router) and b) thus provide internet access to all computers and devices.