Tyrosine and n acetyl tyrosine are better supplements to buy than a mucuna l dopa extract, since a majority of the l dopa gets broken down outside of the blood brain barrier. This is why the prescription product sinemet comes with carbidopa, to prevent this from happening. Unfortunately, carbidopa is rx only, though. I'm not sure about phenylalanine because I've never taken it, so I won't speculate about its efficacy compared to the other two.
I would say yes, the cabergoline would help, as you would have less endogenous activation of your dopamine receptors, and the cabergoline can help compensate for this, at least partially since it doesn't bind with high affinity to all receptor sites.
Chelated magnesium is good to take for its cardioprotective properties, as well as it's neuroprotective ones.