FSX works fine under Windows 10. No worries. Best is to buy FSX Steam Edition, it contains all the fixes and tweaks that need to be added to FSX Boxed to run properly.
FSX will work quite okay on the CPU you're running. The graphics card will limit things though. If you're able, upgrade it to an NVidia card. A 970 or 980 will give nice results for example.
It's true that FSX is a very old sim. It's a 32-bit piece of software for example. Also it DX9 for which is dated. Still, it works okay. But where in the past technology was the bottleneck, now it's the dated code that limits things on modern systems. It kind of passed the optimum of the curve so to speak. ;-)
In that respect it's also an idea to consider to use a 64-bit sim like X-Plane of P3D. It's more future-proof. Personally I'm an FSX user because of the large ammount of add-ons I invested in through the years.
So, yes all works fine with a slightly better graphics card. Yes, Windows 10 works fine in combination with FSX by default as long as you use Steam Edtion instead of the boxed version.
But whatever you do: DO NOT(!!!) install FSX in its default folder but in a manually created folder like C:\\FSX
Grtz., Hans