The reduction in blood pressure is benefical and should not be any concern. My doctor wants blood pressure as low as possible without any side effects such feeling faint, dizzy, etc. An erradic heart rate at rest can be a problem (coreg should correct that problem). Many doctors discontinue prescribing plavix as there is a higher risk of excessive bleeding.
Cardiac cachexia is unintentional severe weight loss caused by heart disease. Even with a very good appetite and high calorie intake, some people with heart failure lose muscle mass. That can be explained as heart failure may cause blood to back up into the liver and intestines, and they may swell. Swelling of the intestines may not allow for adequate absorption of nutrients from the food you eat.
Its difficult to comment on your father's condition as there are so many abnormal affects associated with your father's health...it is has to be frustrating for you and others, but it appears you father is receiving appropriate treatment.