When doing a dual target, can I target an object for 3 and a character ON the object that possess stealth? What the point is, target, I blow up the object for 3 and then roll to hit the character who was once on the object for 2.

No. You cannot target both a character and an object with the same attack.

From p. 11 of the 2010 Core Rulebook:
From p. 17 of the 2010 Core Rulebook:
Also, keep in mind that when using multiple ranged combat targets it is one attack.

Yeah, I just wanted to be completely sure. Thanks

This issue actually came up in a game last week, so I'm glad someone had the temerity to ask for clarification! Looking up obscure rules in the middle of the game is never fun, so we just allowed it (dual targeting a character + wall), but now I know to never let my opponents do this in the future. Thanks for the answer!