Do stop using their trademark or making reference to them immediately and let them know you have done so, ie points 1-3. But, I would say do not agree to any fu

Do stop using their trademark or making reference to them immediately and let them know you have done so, ie points 1-3. But, I would say do not agree to any future conduct in writing on behalf of your business without talking to a lawyer first - I think you need to carefully word a response around that to avoid liability. IANAL, this is not legal advice, etc.