I use an old WRT54G as a bridge. I flashed DD-WRT firmware on it about 10 years ago.. watched youtube and netflix with a device plugged into it as recently last night. It seems to be *much* faster than connecting wifi directly from each device, especially the game consoles.
Very tiny suggestion to use nano for newbies. :) It's a much simpler editor and the commands are right there on the bottom (CTRL-X to save&exit). I use vi, myself, but if you're not familiar with or literate on Unix platforms, nano (formerly pico) is the way to go:
nano dnsmasq.conf
I'd first simply power if off for a couple of minutes and then power it back on. Are there any errors in the log on the comcast modem? You didn't specify which device you have but for many (Arris) it's at http://192.168.100.1/
EDIT: I noticed pptpd running in your logs. Are you using PPTP...
It could be all in my head, but it seems like this router gets slower after it's been up a while. I switched from stock to Merlin firmware a few weeks ago and it seems better but sometimes it feels like it gets stuck a little every so often.
Is it normal to see 98-100% under "nic" when...