Ask Mr. Smarty Plants

For openers, I would find a new source of potting soil. Your problems date from the first bag of potting soil you bought, and the second one didn't look any better. "Sterile" on the bag apparently doesn't mean really free of unwanted organisms. Philodendron bipinnatifidum is not a plant native to North America, but rather of Paraguay and Brazil, so it is out of the range of expertise of the Lady Bird Johnson Wildflower Center. However, will try to find some websites that address both your specific plant, which is a tropical and of potting plants for indoors in general. We sure don't think you should forget about the worms, whether they are harmless or not. Obviously, in Connecticut, this is going to be a house plant and that would give us the creeps, having a worm home in the house with us. Read the information on these websites, applying what is appropriate to your situation. As you work on the plant, wear rubber gloves and be careful of the fluids in the plant, as all parts are toxic. They should not be left where a child or a pet could get to them, and contact with the fluids will cause irritation in the skin of most people. 

Floridata Philodendron bipinnatifidum 

Guide to Carefree Houseplants - follow the link to "Houseplant Troubleshooting"

The Garden Helper Care and Cultivation of Houseplants 

Frankly, at this point, we think you need a major cleanup. In the process, you may get a few more plants, all of which can continue to memorialize the gift. Since it's now summer, the plant could go outside, at least for long enough for you to perform surgery. If you want to preserve the plant as it is, get it out of the pot, and lay it flat on a surface with a water hose nearby. Direct a good strong spray of water at that root mass and get every bit of the old soil off, if you can. This is a very tough plant, and if you want to cut off some upper foliage to make the operation easier, that can be done. It is going to need to go into a clean pot, with new soil. If you want to get some additional plants, there may be offshoots that can be separated from the roots, or you can just divide the roots. We understand this involves a strong sharp tool and some strength. Be prepared to unearth some more of the beasties that have been inhabiting your plant pot, continue to wash them away. There is a recipe for making your own soil in The Garden Helper website above, which you may want to try since you haven't had much luck with the prepared stuff.