Understanding 'Mental Health': What is the Dialogue Between Psychiatry and Philosophy?
I am rather surprised that you challenge questioning the medical model. Also, I am not sure about your division between experience as being subjective and behaviour as objective.
As far as the medical model is concerned it is bound up with values, especially of what is 'normal' or acceptable. This involves ideas and what counts as delusions. For example, religious and spiritual ideas. The cultural context is important. Similarly, ideas of acceptable behaviour are socially constructed. The medical model and science are established by underpinning values, rather than being value free.
With difference between experience and behaviour, the fine line may be the interaction between experience and behaviour. Experience includes thoughts and feelings, whereas behaviour is about how a person acts in regard to thoughts and feelings. For example, a person may experience intrusive thoughts of suicide or harming others and what is critical is the perceived risk of a person acting out the intrusive thoughts.
How a person understands experience is important in itself. Interpretation of experience is not merely subjective because it involves others' understanding, which in turn affects subjective experience.