I own a DS-88 and also use the VB3m running on an android tablet, both are fantastic sounding, but I run the organ app from an old M Audio Axiom 61. I've run the VB3m from the DS-88, but is a pain in butt when changing programs from the DS-88
To get the Axiom to work with the tablet, I use a USB B (out of Axiom to USB C cable In to Tablet), then use MIDI Connector Free app from Google Play store,
Audio (Headphone) out from tablet goes either into DS-88 line input OR direct to my custom Leslie speaker (The BST). Master Volume for VB3m is controlled via Volume pedal if running into DS-88 or from Axiom to BST.
See the attached pic, I'm happy to answer any questions.