And, what's your Realtor doing about it? We're paid to handle these issues.
In addition to Stephen's advice of offering a higher purchase price to cover the cost of the repairs so the seller nets the same amount as you originally agreed upon, have your agent talk to the listing agent. Have him/her offer to meet any contractors doing the work, because the listing agent surely doesn't want to take time out of his day for it, especially if there will be one or more contractors. Even offer to select the contractors (the listing agent will usually say no, they have they're own). Now, at least you're talking. When listing agents say sellers won't do work, they mean the sellers don't want to pay for it, and the agent doesn't want to have to do any extra work. So, have your agent talk with the listing agent before sending any addenda regarding this.
Also, conventional loans are pretty much just as strict as VA or FHA loans regarding repairs. If an appraiser sees ceiling stains, they'll want the cause taken care of, because it affects the structure. Broken windows will need to be repaired because it's a hazard. And, unless the next offer is a cash offer as high as yours, any offer with a loan will likely run into the same issue.
Good luck, I hope it all works out!