Barking in apartment complex

Hey all. I have intermittently posted here looking for advice about my pups behaviours. We are mostly managing things well except for his barking.
It has never really bothered us as he is a “barky breed” (Japanese spitz) and we have had him for nearly 18 months with no one making a peep. Now, having our Bub has actually wonderfully encouraged other people to get a dog in our complex, but unfortunately it has had a cumulative affect of intermittent barking from all of them. Unfortunately, we have now gotten the blame, because our pup can be SEEN while the others are in a front courtyard and cannot be seen…

My question is – can there be anything done with “barky dogs” or are they just that – barky. We have tried a few things:
– calling him in when he barks and giving him a treat (this worked well until he started going outside to bark so he could be called in to get a treat)
– telling him “good boy” when he barks at something correct, and then saying “no” and bringing him inside if it’s the wrong thing to bark at.
– keeping him inside (which obviously works, but he needs to use to toilet, and likes to watch off the balcony) also he still barks if he hears a noise.
– ignoring the barking if it seems to be attention seeking (but he just keeps barking for 15 minutes or more and we would get in a lot of trouble for that).
– teaching him “thank you, quiet” but he still just starts and barks at everything again.
– teaching him “Charlie, on your bed” – which works for 2 seconds then he goes outside to bark again.

He is honestly not doing a bad thing (in my mind) – he barks at people who walk through our complex. I have had 2 bikes stolen, and we have had car windows smashed in the past, and now Charlie stops that as he barks at unfamiliar people. We are just so worried we will be asked to give him up, which is what they are threatening.
Any advice is so helpful. Also, he never barks during the day as we keep him inside – he is honestly only barking VERY OCCASIONALLY in the late afternoon/early evening, but apparently that is an issue..

Sorry for long post. (Also I’ve posted before about how much exercise etc he gets which is ++)