Your fact pattern is like a law school test question because to have a viable claim it must be foreseeable that the landlord's conduct would cause an accident like yours. Given the severity of your injury I do believe it's in your best interest to contact an experienced attorney.
Unfortunately the leading cause of brain bleed behind trauma is anti coagulation complications like this. Whether there is responsibility will depend on how closely he was monitored and whether there were changes in his bloodwork that were not properly appreciated or handled
Generally Medicare claims back 70 % of all amounts it reimbursed on treatment related to injury caused by the malpractice. Make sure that Medicare is not adding in treatment that would have been necessary even if the malpractice had not occurred. Your lawyer should navigate this for you.
The case should have been reviewed by an expert already assuming you hired an attorney shortly after the event. The experts findings in a NY medical malpractice case are often not provided in report form. Instead the attorney gets a comprehensive oral report from the expert and the attorney documents the experts conclusions. Your attorney should then be in a position to report to you the experts findings.
The shoulder is a complicated joint with many different parts. Perhaps a review of the prior records will show that the injuries are quite different. Thus it's best to advise your attorney so he or she can compare the injuries and reconcile them so any damage to credibility will be limited.