Gauging their responses, to me it is evident that they are just stalling. Or perhaps Sharpies have been on backorder at the TSA for the last 10 months since they are no longer premitted to use grown-up tools like computer programs for redaction since SOP-gate.
Also, if they don't reject your request, you can't sue them for rejecting it. If you sue for constructive denial, they'll likely pull the SSI card-- only a Court of Appeals can compel disclosure of SSI-- and claim the District Court cannot offer any relief. Or perhaps they will masturbate with extension motions before the the court (like they have for you via email for the past 10 months) until the court wises up and then move onto a plan B.
Any legal action could easily get tied up in the courts for 2-4 years before even a partial resolution. The legal process doesn't move so fast, does it?
Here is one thing that they have on their side: Time.
So much for the promise of a new standard of conduct when it comes to FOIA requests.
