Even if your mode of thinking was advanced on the level of neurobiology, any psychotropic chemical can have a wide range of effects on an individual. Take alcohol for example--it makes some really tired, and others extremely energized. I know this explanation is a bit reductive, but no more so than what you're proposing.
Maybe a better example is that stimulants make some tired and others unable to sleep. I can drink coffee and fall asleep while others would be unable to.
Generally, dopaminergic agents doesn't induce anxiolysis.
Instead of playing around with your brain, why don't you just let your doctor, who after all went to medical school in order to treat you, know what's going on?
Why do you feel the need to add something dopaminergic to the mix?
Anti-parkinsonian medicines probably won't do that much for you. If you want a "kick" to your medicine, tell your doctor. He/she might be able to prescribe something. As it is, justifying use of a medicine which isn't indicated for depression based on the most basic psychopharmacology will more likely than not set you up for failure.
Not sure what you mean be "anxiolytic feeling even similar to other drugs like alcohol". Alcohol stimulates the reward pathway in your brain, but alcohol and levodopa couldn't be more dissimilar.
Again, talk to the doctor. Let them do the work. That way, if something goes wrong, you don't have yourself to blame.
Does your SNRI work?