Opy, your setup is basically the exact same thing I'm trying to get working. Can you do us all a solid and be more specific about how?
Goal: Get my DCS World 2.5.x working with three identical screens plus a touch screen (with Ikarus preferably, or HELIOS second choice) with interactive gauges and switches in a T-configuration. I intend to fly the A-10C 80% of the time and the FC3 F-15C 20% of the time. All running stand-alone installation of DCS in Windows 10.
Detail: I have three identical 32" flat panel displays at 2560x1440 resolution in a three-panel side-by-side array. We'll call them 3-1-2 (those are the monitor IDs as reported by Windows 10).
I have a fourth monitor that is a 1920x1080 touch screen in the bottom center position, directly below monitor #1. We'll call this one #4, as reported by Windows 10.
This forms a T-configuration, with a 7680x1440 resolution viewport across the top three.
I have followed directions provided in many of the other threads on this forum and that advice has gotten me this far, but I still have a little more to go.
Status: I have successfully got the three main monitors working with a customized 3screens.lua file, and I have been able to get Ikarus to export 90% of the A-10C's cockpit gauges to #4 (they work and interact to my touches). However, the MFCDs and RWR (and maybe some other displays and gauges I'm unaware of) don't display on #4. The OBS buttons around the MFCDs on #4 work; I can press them and their results affect the main screen cockpit.
Frustration: I have been able to get the left and right MFCD and RWR to show up on the three main monitors (3, 1 or 2), using X/Y coordinates to place them where I want. These floating displays 'work' in the sense that they show what's going on in the main cockpit.
However, I can't get them to show up on the touch screen monitor #4 itself. I've tried referencing Y values greater than 1440, etc. I've tried including #4 in the total resolution in 3screens.lua (7680x2520) but that doesn't work, either; it screws up the main displays and still doesn't display the MFCDs and RWR on #4.
Bottom line: How do I get the MFCD displays to show up on my touch screen #4 monitor?