Welcome to the Q&A Forum

effectdigital Nailed it. I couldn't explain it better. One thing I can point out is, once you create the disavow file, update that file and upload. If you have lost your disavow file, download from Google webmaster account and update it, re-upload it.

I would recommend setting up server side redirects from your host with 301 redirects. It can be a tedious job but it's well worth it SEO wise.

Mix your anchors as much as possibly. Build naked links, brand links, generic terms, exact match terms (keep the ratio below 10%), long tail variations, picture images etc. Don't only focus on one keyword or url, that way you'll stay out of Google penalties.

DA stands for Domain Authority. Moz uses the DA algorithm to make a single score for the whole site. The Algorithm takes into account the links pointing to your site, total number of referring domains, total number of backlinks etc. It's co related to how powerful your site is and how would you rank/get traffic from Google.