I am not as qualified as some of the people that will post here, but I use the same stakes to prop up my neps too. I think that your plant looks fine to me and I don't really know if more humidity will make it pitcher more [edit: i think humidity helps keep pitchers around longer]. It looks like it just has climbing on its mind, because it has started going to the vine stage. When it does pitcher, they will be uppers.
You say that you have had it for 3 years. Have you repotted lately? Do it while you don't have to worry about killing a lot of nice pitchers.
I notice too that when my neps start to vine the tend to produce more off shoots that will make good looking lower pitchers once the vine stops climbing.
If you are worried about the light (which it should be good now that summer is almost here) get a clip light from the hardware store and a good high lumen high kelvin bulb. I have 2 bulbs in my window totaling 3000 lumens and it is about as bright as a real cloudy day, but the neps liked the extra juice.
Or just keep it watered and forget about it, it will work itself out, patience.
Hope this helps!