I am not understanding the purpose of springing a piece of rolling stock with four wheel bogies.Hello Playmofire,
May be i have the solution for your wheel turning problem and your decoupling problem as well.
I used to have the same wheel turn problem with axis not returning to their straight position.
I solved it by applying a thin carbon steel wire of thickness of 1 to 1.2 mm as a bending spring.
The wire is fitted into two drilled holes opposite to each other, one in de rotating wheel construction
and the opposite end into the basic structure of the train car. Both holes are at the same level
so the spring can move free.
After each turn the wheel axis is turned back to its straight postion. This is also a great advantage when
you must put the car on the rail, especially with cars having double axis at each end.
See the pictures as examples.
About the decoupling problem using two hooks. I buil myself a simple item from flat 2 x 15 mm aluminium
with one leg 10 cm long perpendicular to the other of 80 cm long. using this i can decouple from a standing position.
I use this item also to pull and push cars when necessary !
Have a nice day !