Hold on.

My rig is excellent

Please, no need to be smug about it. You're running a dual core Ivy Bridge, that architecture is about 5 CPU generations old now, and with only dual core - (4 logical processors?) and old physical hardware - I can about 98% assure you that the core is your problem.

I chose this CPU because it has a very high core performance, faster than early I7's

You must not build many PC's - it dosn't matter what you buy or how it is when you buy it, it'll get revised many times over it's life cycle, and will eventually be succeeded by better cheaper hardware that works with (generally) better software.

Besides, a lot of people have hardware much weaker than mine

And those people are probably playing consciously of that, not demanding the core overload on physics calculation with ~2000 part ships.

and also don't have the money to upgrade.

well, I got bad news for you. (I can assume your core was manufactured in 2012/early13, because that's when the Haswell architecture succeeded Ivy Bridge) your core is older and you're demanding a lot of work from it. You may have already done damage to it, especially if you've tried overclocking it.

I personally had a core get damaged from over working it, it continued to work after being damage - but was very unstable including being easier to clog up with processing and only working with 8 gigs of ram. I seriously recommend you stop beating your current core until you can get a new one.