Have you tried with the Skippy? It's obviously very car dependant.
By the way I'm talking purely about slip angle here, I quoted a little to much of your post to make that clear.
The tools are out there (i.e. my telemetry plugin and an app that can graph the data from csv files, Excel will do if you don't have ATLAS) for anybody to try this for themselves and attempt to correlate what they're feeling at the wheel with the data that the sim is outputting.
Finally i could find some time to drive the skippy national and you wan't really know what i think about that car, but to stay on topic about the steering feeling, the result of the driving emotion is that it is one of those better feeling cars in rf2 with the T500RS but there is also nothing like a slip angle to feel, a lot of alignment forces, but less load distribution and lateral acc feeling, and very little brake forces on the steering.
Than i had an idea, if that could be the alignment forces that are to dominant here and kill all the dynamic and feeling in the steering wheel, and jumped in the cockpit of the EVE F3, because this car allows to reduce the caster to zero, and the result is exactly what i tought, alignment forces are the ones eliminating the details, but this setup also shows the lack of lateral acc and weight distribution feeling on the steering, even if the result is 1000 times better as with high caster values. Of course it is not the optimal value to have the caster at zero or the final setup, but good for this test.
The tires may are not the best choice to rate the quality of the tire and ffb physic in detail but it gives me and idea, not at least because i guess they are very close to street tires letting me feel more at home. The overall feeling with this test was already very impressive, apart from the mentioned things above where i think it is somewhat weak in, i also miss the depth in steer bump feeling this cars had before some builds ago ( i think 860 ), but i could feel something like a slip angle, and how the grip is increasing and decreasing under load, as well as the brakes lock the steering before the tires start to slip. The steering dynamic was also very good with the T500RS, if not the best in this sim. How detailed the car reacts on bumps even under unequal load and transmits this to the steering is great, but it anway don't does this on straight drive, as if the vertical offset does not move the steering arms anymore, and also the response to rutting or inequalities or how it calls is almost dead. This was better builds ago, otherwise i would say it is one of the best cars in rf2, the gfx are cool, the cockpit emotion is great, and has the best overall driving emotion for me so far.
My conclusion is that this car don't needs much work to be perfect on the steering wheel, how realistic it is i don't know, never driven such a thing, but it is very believable to me.