I am currently using 40g coffee to 500g water which is 12.5g coffee to 1g water but I have seen things like this https://www.olympiacoffee.com/blogs/blog/how-to-brew-like-olympia-coffee#:~:text=For those of you who,use 16.7 grams of water. which suggest using a little more. Does it even matter to adjust the ratio precisely if I don’t have a precision grinder and am using a Krups blade grinder? I am trying to get things as precise as possible.
You reversed your coffee and water in the 12.5:1 portion.
Measuring is important for repeatability but getting a good grinder should be your highest priority. A Timemore C2 will be a huge improvement over the blade grinder. You should be able to find one for around $60 most places.