I know Vader needed the life support system in his suit to live, and he was already partially depending on the force to survive. But with the masking technique that the Sith Lords sometimes use. Was there canon indication (based on Vader himself as well as other Sith powers known) that he could have left the suit and restored himself?
As previously mentioned, in Shadows of the Empire, Darth Vader was able to harness his anger to breathe without his suit for up to two minutes at a time. His issue was that every time he was able to breathe without pain, he would feel joy or relief, which would dampen his anger. It was his anger that helped fuel his Dark Side healing techniques, so he was basically handicapping himself by feeling joy at his success. If Vader had managed to maintain his anger long enough, he could very well have healed himself.
While Vader was able to heal himself to some degree.. overall, healing energies are not a strong suit of the dark side by any means. That is something that is typically in the area of the light side, which is why many Jedi such as Yoda, Ikrit and others lives for hundreds of years.
The light side sustains life, while the dark side steals it and takes it away. The same generally goes for healing as well. Though other Sith Lords, such as Darth Caedus (Jacen Skywalker) was able to heal himself of pretty serious injuries using Jedi healing trances, overall it's a good bit harder for dark side users to heal than light side users.
I personally believe that the only reason that Caedus was able to heal himself from the serious injuries he got when he fought, and almost lost to Mara Jade Skywalker, was because he was not fully turned to the dark side yet, so he still maintained enough light side power to be able to effectively heal himself.