You will solve things by plugging them in directly to the modem IF your ISP allows you to have two simultaneous ip addresses. Most don't unless you pay for a business connection and/or multiple IPs.

The 172.27.35.1 is the LAN IP address of the Ooma router. Your Linksys router has a WAN IP in the 172.27.35.x subnet. You need to figure out that IP and forward a port - say 9091 - from the Internet on the Ooma to the Linksys router's 172.27.35.x. Then you need to forward port 9091 on the Linksys to the 192.168.1.147 and port of your camera.

This called double NATting and can cause some odd network issues. It should mostly work, however. A better solution would be to use your Ooma config interface to set the Linksys router as a DMZ host. This means your Ooma just passes everything from the Internet that isn't related to Ooma to your Linksys as if the Linksys were connected to the Internet directly.

As for the ports you investigated being closed, those are likely the ports that Ooma is connecting to at ooma's site, not inbound ports for your network. Still, I wouldn't use common ports like 443 because those are the first ports that people scan for.