everything is possible with Voicemeeter! just need to be used in the right way.
(1) All sources may be connected to Voicemeeter.
your MIC on hardware input #1 = ok
Skypke caller on hardware input #2, through VB-CABLE = ok
you Desktop audio = PC-Sound , should go to Voicemeeter virtual input.
set Voicemeeter virtual input as default playback device to do so.
(2) Voicemeeter outputs are driven by BUS.
your realtek headphone as output A1 is used for monitoring = ok.
check that skype source (Skype Microphone) is selecting Voicemeeter virtual output (BUS B1).
OBS could use Voicemeeter AUX output as audio source (BUS B2)
(3) assign your different sources to Busses thanks to BUS Button (A1.., B1...).
to understand how it's simply logical, you can also follow the user manual step by step until the USE CASE #1
http://vb-audio.pagesperso-orange.fr/Vo ... Manual.pdf