Ok I will relent in providing an answer.
Your CPU and GPU are capable of running X-Plane. You have created your problem with the statement made in your opening paragraph.
X-Plane 11 is more resource hungry than XP10. You need to run XP11 from a dedicated graphics card and not from the motherboard. This has already been stated in an earlier posting from a Laminar Research staffer in this forum.
By connecting to the motherboard the CPU and GPU are "sucking off" the power of the motherboard from each other and your current problem exists.
Install the NVidia software and configure your system from this system. Forget windows.
Read chapter 3 of the manual which can be found at https://www.x-plane.com/manuals/desktop/#preparationandinstallation
I see you have 3 options.
1. Connect your X-Plane monitor to your graphics card as it should have at least 3 outlets; or 2. Purchase and install an additional graphics card and do not link both cards through SLI; or
3. Purchase a new computer to run X-Plane
For steam problems you can also go to the X-Plane.org site. This site has no connections with Laminar Research (X-Plane.com) or this forum site.