The Esellerate engine not found error is caused by having mistakenly set FSX.EXE to run in “Compatibility” mode (like Windows XP under Windows 7/8 or Windows 7 under Windows 8/10), which is not how FSX defaults to and it reduce performances.
Turn off every compatibility option in the file Properties for the FSX.EXE program.
Also, be sure you don’t have other 3rd add ons that start with FSX and runs in Compatibility mode, because they might have the same effect as if FSX itself would run in Compatibility mode too.