Deathstroke's age in the comics is a bit fluid. It often depends on the creative direction of the story. Usually, he's thought to be in his mid-40s to early 50s.
The Deathstroke and Batman comics are related in that they frequently encounter one another in the DC universe. Their battles and partnerships shape the comic narrative, and their distinct personalities add depth and excitement to the stories.
In comics, Deathstroke is typically shown as a cunning and powerful adversary for Superman. Superman, on the other hand, embodies moral righteousness and superhuman abilities. The clashes between them make for exciting storylines.
Sure, Deathstroke can show up in Suicide Squad comics. It varies though, as his involvement is based on the creative direction of the writers and the needs of the plot.
You should go for 'The New 52: Deathstroke'. It presents a modern and engaging portrayal of Deathstroke. Another one is 'Teen Titans: The Judas Contract' where Deathstroke plays a significant role and it's highly entertaining.