Okay, here's my 2 cents. I know a lot of good little guys, I have one(I'm kind of patial to females). I got him at 5 1/2 mos and had him neutered the next day, he's great, hes also pee pad trained and stands and actually does better than the girls, when he goes outside, he also likes to lift his leg then. Now, the neutering doesn't always work, unless you get it done before he starts lifting his leg. My sons little yorkie was neutered at 5 1/2 mos. he started lifting his leg at 12 weeks, and to this day(almost 2 years) still does. I make them put a belly band(I bought) on him over here as he's always lifting his leg in my house. the pad in the belly band is soaked before he leaves.
I probably would have rehomed him if he was mine, i can't handle that marking. good luck on whatever you decide. I would def. try and get him fixed before he lifts his leg though.