VUS have much less outright grip than the 050A. It's the 040 Bridgestones that are no good, the 050A is a great tyre.
You've currently got a car with lots of grip at the front and not a lot at the back, relatively speaking. It's going to make it very easy to oversteer, which is why the TCS is kicking in frequently. The VUS is a good tyre, particularly in terms of feedback, but it's not as good as the 050A in everything else. Either match the fronts and accept lower grip levels with a lower cost to replace them, or get another set of 050A for the rears.