curling the markup is not for realtime. sometimes you can get away with curling in a loop with some sleep, and depending on the latency / scale you will get the same effect. however blessed-contrib can also be used as a server side component where clients curl for its endpoint (which is different than curling a static markup). that way it can return a live stream of data. you would use the same approach as https://github.com/yaronn/wopr/blob/master/server/server.js#... where your present method implementation will run in some loop / timeout and keep sending data (by calling screen.render).
You don't even need to do that, just using a box-drawing character where half the character is black (U+2580 or U+2584) would double your vertical resolution.
[1] https://github.com/yaronn/blessed-contrib