Thanks for the pics. I do like imafan's suggestion, if that is getting to be too much cactus to keep in the house, you can take a cutting and start over. You said elsewhere that your are in northern New Jersey, so clearly the cactus needs to stay in for the winter. In the spring when you take it out would be a good time to start the cutting, then you can just fail to bring the big one back in, this fall.
Nothing else you can do is going to make what you have any shorter. For future reference, the more light and the less fertilizer you give it, the more compact it will be. It sounds backwards that more light keeps it shorter, but as already stated, plants stretch for the light. You said it gets direct sun, but it is sitting in front of a blank wall. Unless it was just moved there for the picture, it's not getting much direct sun. If you start that cutting, put it right in front of a good south facing window and/or put a lamp directly on it from a few inches away. That should help it stay more compact. And cacti should be in a cactus mix soil which is very sandy and mineral and need little to no fertilizing.