"Push self towards (direction of movement - 180) at force x" must push them in the opposite direction of where are they moving, if you calculated direction of movement correctly. I know it work, I do it in my project. Direction of movement is not "direction of self", instead you need to calculate it.
There is no need to calculate force, use simple number (at least first, to check if it works). The objects will appear to slow down in a natural way.
Edit: one more thing - you want to add something like "if speed > 0.2" around the hole "push self" block and "otherwise set speedx and speedy to 0". Without that it might be pushing object even when it wasn't moving. To calculate speed use sqrt(x-speed^2 + y-speed^2).