The coughing certainly could be a sign of heart disease. There are meds that can help that in many pets and perhaps yours could benefit from them too. If his heart is not working right his kidneys and bowels may also not be working right.
The excessive drinking and urination can be signs of kidney disease, diabetes, or even Cushings Disease which you can read about here
www.marvistavet.com/html/cushing_s_disease.html
If he seems disoriented this could be from heart disease or liver or kidney problems or cognitive disorder.
You really should have a vet see him to determine if the problems are ones that still can be helped or not.
You can read about heart failure and treatments here
www.marvistavet.com/html/ body_heart_failure_therapy.html
Hope this helps you and good luck with him!
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