Since he is 4 yrs old and 1400g, the hunger strike may have more to do with the time of year than any security issues, in which case, stuffing the tank won't help. Since we are pretty much at the end of the breeding season, it is likely your snake will start to eat by itself soon. Just keep an eye on the weight, and if it starts to lose a lot of weight, that is when you should get worried.

In the meantime, it doesn't hurt to try to eliminate any sources of stress. Double check your temps & humidity, make sure tight fitting hides are available, etc.

Stuffing or cluttering up the tank won't hurt. The idea is to make it so the snake feels secure and partially hidden even when not in its hide. You can crumple up newspaper and cover the bottom of the tank, or add lots of fake greenery from places like Walmart or the dollar store.

Some people feel that a medium rat is too big of a meal for a BP, but it is hard to be sure what size you were feeding since "medium rat" can mean very different things from one pet store to the next. You might try a smaller size, but there probably is no point in going all the way down to a pinkie.