Need advice (unemployed and need to land this offer): how are these answers for a County Employees Retirement Association interview?

My advice without knowing the role specifically or your CV. 

• When asked about your own experience, flip your chronology around. Tell your story as concisely as you can, highlighting the key experiences/skills/value that you will bring to the role - ending with your most recent experience. IMO you want to end with them seeing the most experienced, valuable, 'today' version of yourself vs. where you started - that will segue, IMO, to you mapping all of the skills and experience you have, to the role you are applying for.  
• Focus on crafting every bit of your story and experience, to what it allows you to bring to the specific role in managing/overseeing the county's retirement funds. Less on each specific role, more about how each role + your MS + your CFA have contributed to the knowledge you will bring in helping the county prudently manage it's investments.
• As to the 'why this job and entity' - if you are truly passionate about serving the public and the community, I'd lean into that. Public sector entities, specifically pension funds that are often underfunded in the first place, need smart professionals like yourself involved. Those funds, and returns, both benefit the community and are relied on by their recipients to live their lives - given the wave of tenured, senior professionals retiring - it's a real issue across the public space to fill these roles. Obviously, don't go over the top or be disingenuous - otherwise, you are on the right track on that. 

As always, I think the key parts are linking your experience to the role you are applying for as well as knowing as much about the entity as possible. Make sure you've read through their financials, have an idea of their financial situation, what investments are there today, etc. - every little bit counts, even if you don't necessarily use it in the interview.