Is the purple after the blue the highest schematic you can achieve?
I understand that you have a chance to create a better purple with an augment slot.
What does companion affection do in Swtor?

As far as I know there is not point in R/Eing purple items aside from getting some of the mats used back if for some reason you can't sell or find some other use for the item.Augment slots are a critical success on making the item, so its just a random chance whenever you make the item.

Companion affection does a few things. First it opens up extra dialogue options with the companion, basically mini quests that give you background information on the companion. Sometimes those will turn into a mission and eventually going through the dialogue options will open up relationship options with your companions. The other thing that affection does is it increases the companions crafting skills, it definitely adds efficiency and most likely also add crit to any crafting skill they are assigned to, on top of their normal crafting skill bonuses.