Hi Pawel, glad you like it!
It's totally possible to have so many wheels. Actually you can only have 4 wheels but each wheel can be made from multiple wheel components ( as long as the two wheels on the same axis are symmetrical in position and shape). I have done a lot of playthroughs already and i try to make my rear wheels at least 2x3 for more grip, especially in the new version with burnout/traction loss and mud this comes in handy.
I think you were unable to walk because you were carrying too much. If you can exit the car (see the player/'X' next to your car) and are unable to move without being blocked by other objects it's most certainly the case. You can see if you are overburdend in your inventory window. The last line says something like 11 / 10. Which means you are carrying 11 weight but can only support 10. It also turns red if you exceed your capacity. Then you can either drop items (they just disappear) using right-click in inventory, or you enter your car again and build some components into your cars design to get more free space. Also for each trunk component you add to your car you get +2 maximum carry capacity.
If you still have questions or find any bugs feel free to ask/tell me. Your feedback is much appreciated!