This is good :)

The sense of tension you describe seems to me more like a sense of dread, but I can see how someone might think it is tension. Given the limitations of chiptune music, that's not easy by comparison to other genres. The energy is very action-oriented, like any good 80's NES game.

I think the abrupt ending is an incentive to change the file playback mode from "song" to "loop."

The mix could be a bit louder. You may want to try using a compressor and/or limiter, or simply normalizing the track so that the listener doesn't have to change the volume just for this song.

More info about how I review music here: https://codefreq.newgrounds.com/news/post/1089806