What a cutie!

Since he isn't housetrained yet, is there any way that you can crate or gate him when you are not home? Having free run of the house while not housebroken could be confusing to him. By crating or gating him to a separate room (ie kitchen) he is less likely to have accidents as he might feel this is "his" area. Crating or gating also makes dogs feel more secure.
Sounds like the treats when he goes outside is working. Keep that up! Continue taking him out whenever you can and give lots of praise when he does go.
Hope this helps.