Freewheel Tool advice

Loic, I had exactly this issue with an old freewheel and that tool. I used an old coarse sharpening stone to grind the teeth down. I would lend you the tool but I destroyed it, and the freewheel, as it turned out to be seized on too tightly. Use penetrant spray. Secure the tool before you turn it, and be careful as you start to untighten because the diameter of the tool is slightly smaller (or larger, I forget) than the freewheel it engages and is liable to slipping.

Ah! I am really glad to hear that I am not alone in that situation!
When back home yesterday evening, I checked the tool on the other freewheel I have, on the wheel that needs spokes to be replaced... And it is the same problem that with the shimano 600 freewheel, the teeth of the tool ater too wide...
I will file this down with a dremel, try to find the tighter adjustment / tolerance, and do as you say... I won't be able to do it before january now so I will leave some WD-40 sitting on the freewheel in the meantime...

Thanks for all your contributions guys!

Loic