It will take a ton of trial and error to get it as exact as you seem to want without a part print showing the dimensions and geometric development of the shape. In my career I have had to take 2d client part prints where no model was created, for things like fans and fan shrouds, they generally develop the shape with a set of equations and possibly also translating that into a huge point chart.
I worked for a mold maker and I had to use those prints to make the 3d model that was used to produce the injection molds, so it had to be absolutely precise. I was working on site with full blown CAD software worth between $5k and $10k, and so there were lots of tools to automate the process, but still it can’t pull a rabbit out of a hat, your precision is only as good as the precision of the data, and a picture just isn’t precise data.
If the fan already exists, a 3d scan can replicate the point chart fairly accurately, but that is expensive unless you have the capability in house. What do you need this model for? At the end of the day, if you aren’t using this 3d data to actually cut or print a functioning fan, you might just need to accept a bit of error in the visual comparison.