Notice how when playing spiccato:
– the bow stays close to the string.
– the down bow and the up bow have a similar trajectory, that is they lift roughly the same distance above the string at both ends of the stroke. If the down bow lifts too high the up bow has to travel too far to start the next note and vice versa with the up bow.
Practice this variation using reverse bowing (starting up bow) to illuminate any large differences between the up and down bows.
Use the side of the hair and since the tempo is relatively slow don’t play too high in the bow. Find a stable contact point where the sound is reliably clear.
The use of the right upper arm is just for crossing strings.