Suing the developer due to smell and other issues

Don’t be mad but it sounds like you did not do your due diligence and have the property fully inspected so getting them to make the fix may cost you in time and legal fees if it is not clearly outlined in the contract for sale. I have a Brownstone and there are 6 “party wall” courses of bricks that separate our house from the one next door but when we purchased the house we repointed the entire party wall on our side. That is not to say we haven’t smelled a thing or two (one time the top tenant next door had a fire and we were the ones to call the authorities). We also installed spray foam insulation and a vapor barrier before re-installing sheetrock and that has made the difference. I do hope you find a solution but wood frame houses are tough.