How to make car land on 4 wheels and maintain speed?

So I have made a simple physics for my car game. It is a top-down racer, similar to NES era games, here's a screenshot for you to get the general idea - LINK

You can drive the car forward/backwards with standard acceleration, but driving to the sides is like strafing, the car doesn't turn to the left/right and it doesnt rotate in these axes. The only axis which he can rotate is X, that means it can rotate forward/backward (like when driving uphill/downhill). I didn't want the car to rotate like crazy (too easily, too fast), so I wrote a script that stops the rotation to some extent:

 if (transform.eulerAngles.x >= 30 && transform.eulerAngles.x < 90 && !IsGrounded()){
     rigidbody.AddTorque (-7*Time.deltaTime, 0, 0);
     }
 if (transform.eulerAngles.x > 270 && transform.eulerAngles.x < 330 && !IsGrounded()){
     rigidbody.AddTorque (7*Time.deltaTime, 0, 0);
     }

Visualization if you don't understand what happens - number 2 and 4 - CLICK

It works fine, except for when the car hits something with high speed when it is rotated (number 3 and 5 on picture above) - the force that gets applied to the rigidbody during collision is so high that my script doesn't stop it (because it adds just a moderate amount of force - otherwise it makes things even worse). Yet another picture: CLICK

Even though I blocked the car entity from rotating in 2 axes, I can't do it in third, because then it would be impossible to drive uphill/downhill

I wanted to know if there is a way to make the car land "gently". I don't want to use preset rotation, resetting Quaternion or force values, because that makes the car "jump" to that setting in 1 frame. If I add yet another limiter similar to the script above, it is band-aid solution, because if force is strong enough it will overcome the script. I tried adding manual rotation control mid-flight, but it doesn't stop the player from rotating the car into the "flipping" angle. If I limit the rotation by a script (sorry for pseudo-code, but I can't find it):

 if(rotation > 60){
     rotation = 60;
 }

It often makes the car stuck in this angle. I thought a solution might be something like this - CLICK

but I have no idea how to implement box colliders with constrained global rotation attached to the car, and I don't even know if that would work

I just came up with that script, which seems to solve the problem in a lot of cases, but still if the force is too big it seems to either fail or make car lose forward velocity entirely (which I want to keep - car drives at speed 20, falls down, lands with angle 55 degrees rotated forward, continues at speed 20 or slightly less - a picture of it - CLICK ):

           if (transform.eulerAngles.x >= 30 && transform.eulerAngles.x < 90 && !IsGrounded()){
               if(transform.eulerAngles.x >= 60 && transform.eulerAngles.x < 90){
                   transform.eulerAngles = Vector3(59.0, 0.0, 0.0);
                   rigidbody.angularVelocity = Vector3.zero;
                    rigidbody.AddTorque (-10*Time.deltaTime, 0, 0);
                    Debug.Log("301");
                   }
                rigidbody.AddTorque (-7*Time.deltaTime, 0, 0);
             }
         if (transform.eulerAngles.x > 270 && transform.eulerAngles.x < 330 && !IsGrounded()){
             if(transform.eulerAngles.x <= 300 && transform.eulerAngles.x > 270){
                 transform.eulerAngles = Vector3(301.0, 0.0, 0.0);
                 rigidbody.angularVelocity = Vector3.zero;
                    rigidbody.AddTorque (-10*Time.deltaTime, 0, 0);
                    Debug.Log("301");
                 }
                rigidbody.AddTorque (7*Time.deltaTime, 0, 0);
             }

I am open to suggestions, I've started with unity 4 days ago and I still don't know some basic stuff, forgive me if it has been answered (probably didn't know the right keywords). Thanks for reading :)