ERT gives St Pancras-Brussels Midi as 373km, Brussels Midi-Amsterdam C 212 via the HSL.
Paris Nord-St Pancras is 492.
Paris Lyon-Dijon-Basel SBB is 525, and Basel SBB-Zurich HB is 91.
Routes through Germany are a bit messy, even in the ERT.
Routes can vary, some going via Frankfurt Hbf or the Airport, or even the classic route along the Rhine.
Basel SBB-Frankfurt Hbf is 332.
Frankfurt Hbf-Koln Hbf is 180 via the HSL, 221 via Koblenz.
Koln Hbf-Arnhem C is 163, Arnhem C-Amsterdam C is 96.
You need the ERT for the detail. There is an e-version at a lower price than the printed edition.
The Schweers atlases are the ultimate reference in DE and CH (also AT, SI, IT), giving precise distances from the original sources.
I haven't got the Northern France volume but it probably covers your French mileage.
For online sources, there's a very useful series of wiki sites covering specific railway lines in Europe.
For instance, this is the page on LGV Sud-Est (Paris-Lyon):
https://en.wikipedia.org/wiki/LGV_Sud-Est
This is the English version.
However, there is often much more detail in the local language:
https://fr.wikipedia.org/wiki/LGV_Sud-Est
This includes things like kilometrage and line speeds.
You can always translate the French text to English using your browser, but beware it can go haywire on the columns of data typical of railways.
This is LGV Nord (Paris-Lille-Calais) - again, there is more detail in the French version than the English:
en.wikipedia.org
fr.wikipedia.org
The classic railway routes generally use old names going back to when they were built.
eg this is the Mannheim-Basel railway (built by the Grand Duchy of Baden):
https://en.wikipedia.org/wiki/Mannheim–Karlsruhe–Basel_railway (English)
https://de.wikipedia.org/wiki/Bahnstrecke_Mannheim–Basel (German, note the detailed km data in the route diagram)
You can often hop from one route to another using the links on the web page, rather than searching again on wiki.