[slotloco]

Fronts do look like the stub axles pivot. Should I try to increase the amount by which they do?

Those  stub axles are a pain, because the short shaft attaching them to the chassis DOES pivot. It means they and move around, and they do not create a stable platform for the weight.
My suggestions are
1) Look to see how much gap there is between the outside of the chassis and the wheel - it is that gap which enables them to pivot, and you should try to eliminate
2) Look at how far inside the wheel arch the wheel currently sits as you do want them sitting as wide out as practical
3) As the short shaft mounting the wheel is smooth, they can be pulled off that shaft for truing if you desire, but in any case, carefully removing the wheel, inserting a spacer that removes the "slop" which enables pivot when pushed back in place, will help stabilise how those wheels sit.
4) It is worth using whatever method you can, to glue and true those fronts, bearing in mind you still need them to touch the track and rotate when the car is on the track.
Especially with that front motor weight, creating a tripod which had the front weight all on the guide, and the front wheels not touching, would be a very bad idea!