The Amate variety of Schefflera is a big improvement of over other Schefflera species. They are much hardier in lower indoor light, more tolerant of watering lapses, and resistant to pests. Good choice!
I do suggest that you move yours back a bit d from the west window so it is just beyond the reach of the afternoon sun.
Keep it in its nursery pot and let the top 1-2 cms of soil get dry before watering it thoroughly, however often that may be.
None of your plants benefit much from increased humidity, although it is commonly recommended. It does no harm and bacterial infections are very unlikely. But it is not necessary even in the very dry winter air.
Fertilizer is overrated. For your plants that are healthy and growing vigorously, you can use a standard fertilizer diluted to half-strength no more than once per month.
Online you will find lots of extraneous information about plant care. However, if you simply stick to basics - providing appropriate light and water - you will have few plant problems.