To clarify this: His power affects him specifically. He speeds or slows his own personal "time field."

So yes, he's mostly a speedster. He can slow his personal time too, but that's really only useful if he's waiting for something and gets impatient. 

Yes, "time burns" are things that happen to him. His desync is variable, see. He can do it at different levels of intensity. Desyncing too far destabilizes the atomic structure of things inside of his time field. That means him and anything he's wearing or carrying. The greater the desync, the more unstable atomic bonds become, which can lead to even minor impacts causing severe damage. 

If he's desynced far enough, wind resistance alone could be enough to cause road rash like marks on him. 

That is an incredibly extreme case, though. 

And yes, he is a Titan.