FIrstly, there is no such legal term as a "mother-daughter". A "mother-daughter" house is, essentially, a legal one family house together with an illegal apartment. Building Department Inspectors are entrusted with investigating illegal conditions. Do you have to let them in? No you do not. You will then likely be cited with a violation for "failure to provide access". An Inspector may procure a search warrant if they choose to do so, but they normally will go that route only if it appears...
In New York, when a husband and wife purchase real estate, and the Deed is silent as to the status of ownership, they are, by default, deemed to own the real estate as "tenants by the entirety" where upon the death of one of the two spouses, the then surviving spouse shall be, the sole and exclusive owner of the entire real estate, without exception, provided that they were, in fact, married at the time of death of the first spouse to pass away.
The removal of your wife's name from the deed should have been effectuated at the time your divorce was finalized. Did you question your attorney as to why such a significant task was not finalized at the time if your divorce? With her not being local you may have a large task on your hands.
There is joint and several liability for the tax as well as the penalties but normally it is the title agency who is entrusted with paying the transfer tax on a timely basis. I would suggest that you have your attorney who represented you on the transaction pass it on to the purchaser's title agency to resolve because no doubt they are the culprit.
Required? Why don't you simply contact the surveyor who performed the services for you, who you, no doubt, paid to prepare the survey for you. Meanwhile, this will also give you an opportunity to discuss directly with the preparer of the survey, that being the surveyor, any issues as to the survey.