For a self-identified beginner, you have done very well! Moving Pothois cuttings from water to soil is a difficult transition, but you seem to be managing it very well. The rooted cuttings will put most of their energy into further developing the roots and only later will the stems start to grow longer. The fact that the roots are still healthy is all that matters. Keep on doing what you have been doing and resist the temptation to periodically check on the roots - no more digging around! They are best left alone.
Attempting to replant it now or replace the soil is very risky. Your Pothos seems to be doing fine in the soil it is in, so there is no good reason to change it. In general, the less roots are disturbed the better. That also means repotting is also rarely necessary.
No need to be worried about the critters in the soil.
For future reference, if you do need to repot, use a packaged potting mix that is soilless and contains only peat moss, coir, and perlite.
Below is a Pothos that has been in its original 8-inch nursery pot for 5 years, but has been pruned regularly to keep it full and compact.
