best process from scan image to detailed vectorisation

Hello

I'm doing laser cut of maps, so I have a scan of an old maritime map and I need to vectorise it in Illustrator. The image is yellowish and there ae a lot of writings (names, depth, headings...) that I need to keep and engrave at the end. Unfortunatly I cannot succed in having a decent result, the vectorisation is hawful, just big splashes, as I need to keep the coast line true and be able to read the engravings.

Also in the full map the "white part" color is not consistent, so I spent hours cleaning it, is there a way to do it quickly?

So if someone could propose a process to do it... Thanks a lot.