New (to me) 14" lightweight

Hi all

Time for a new project. This is my first powered cylinder mower and my lack of small engin  knowledge is showing.

Two issues and two general questions.

Issue1: engine  only  run  on full choke. The moment i barely crack the choke it stalls. I cleaned the carbi (it was filthy inside). No change to performance. I did notice the long brass piece in the carbi was very tight and had to be coersed to get down ito the correct position but i got it in. can't imagine this is the issue  

Issue2: engine wont shut off even when throtle lever is all the way to the right.

Question 1: ive read elsewhere that modern  2 stroke oils are such that you should run your mix leaner than 25:1

Question 2: After removing the rust from the cooling fins, what do the cool kids apply to stop rust reforming? I was thinking fish oil or bluing solution.