I will answer in short.
The forces themselves propagate at c. So, say an object is moving at speed v. To speed it up, we have to apply the force that acts faster than v. When speeds approach c, the forces become ineffective in the direction of speed. The forces can work in other directions, for example, the object can be slowed down. Think about trying to push a car with your hands, when it is already moving at 300 miles/hr. You can not, because, you can not move your hand faster than the car. Same way, the forces act through space and nothing in space can be faster than c. This is the reason nothing can move faster than c.
Because objects can move at any speed up to c, therefore c is a speed limit for objects.
The next question can be why forces can not act faster than c? That takes us to next part.
For light and waves and fields, it is not a limit, it is a property (of space). A wave speed depends upon the medium. Space being medium for EM waves, defines their speed. It is a property because the waves can travel only at c, no less, no more. Same way, speed of forces is also a property of space.
The speed limit comes out of relativity theory which is fully proven, and secure theory.
Your points about quantum particles pertain to a part of quantum mechanics that is not yet proven and is highly in-secure (and therefore defensive). This part is entanglement/spooky. Most of QM is very successful and makes common sense. That includes uncertainty principle, computing averages, wave particle duality ... pretty much everything except some of the nonsense like spooky and going back in time. These parts are mathematical speculations and most likely do not pertain to reality. So, they do not mean any FTL either.