Another thing I wanted to mention is that there is no food source for the rat. The only thing I can think of is the bird seed which my wife fills up the feeder and then throws it on the ground also. The pellets containing brodifacoum will take about 5 days to kill the rodent. Dominant rats in a group will hoard bait for themselves and other rats may not get any until the dominant one dies. I would continue to bait for 2-3 weeks.
Shelter is a big draw for rats under the house.
Why don't rats come out of the walls. There are many food sources for them out of the walls, and they could easily access them. But they don't. Or atleast, they don't appear to. They are probably using the walls just for shelter.