DrWhoCares
I worked in the business long time ago. Your scans have enough quality to use png. Just use "256 colors", "max compression", "filter: none". Of course only for b/w pages. For colors it usually jpeg 95% quality.
Just tried for few pages - up to triple size reduction without losing details. Used just simple soft as well, "FastStone Photo Resizer", on already existing pages, with direct saving maybe will be even better results.