I am assuming that you did not have an attorney representing your interests in this deal. If you did, you should contact the attorney immediately. No attorney would have gone ahead with a closing on "assurances". Your options may depend somewhat on the various communications, notices, and agreements of the parties. You should take your paperwork to an attorney.

What you have described sounds like a complicated -- but, unfortunately, not uncommon -- situation following closing where certain promises/representations were made in order to get the closing to occur, but are not thereafter fully honored or, in some cases, even enforceable. The answer here almost certainly depends on the precise terms of the P&S agreement; including whether representations prior to closing made as to the "defects" -- and any agreement as to how they would be addressed thereafter -- actually survived passage of the deed, and/or could have been (arguably) rendered unenforceable by the concept of "merger" due to the passing of the deed.

This is a complicated analysis heavily dependent on all of the surrounding circumstances. A detailed review of the closing documents and the facts/representations/agreements is necessary to further advise you concerning this, unfortunately.

I agree you should quickly consult with experienced counsel, beginning with any closing attorney you hired to handle this (if any), but not necessarily limited solely to that attorney. In my prior experience with these issues, these situations often raise potential claims extending beyond just the seller/broker depending on the facts. Feel free to contact me directly to discuss further.