I always have a ton of extra coins. Currently about 1/3 of the way through chapter three.
My town currently:
-13 Residences. 6 are level 8, 6 are level 7, and 1 is a Magic Residence at level 3.
-Culture is 170%. I always aim to have enough culture to hit max since this helps with coin, workshop, and goods production substantially.
-Main Hall is level 7. I usually only have a few people a day help out with my main hall, but the higher level helps collect a lot more when helping out others. I usually only upgrade the Main Hall when I am capping out really easily and really frequently.
Not sure what level you are, but I have 2900 in population, so pretty close. 820 of those are from a Glossy Gardens and a Well of Floating Islands, so my guess is that I have a lot less residences than you. Definitely shift your focus on upgrading fewer residences, the main hall, and upping your culture for better coin production.