Those values are pretty hard to determine. First the real data is strictly classified. Second it is hard to estimate how it would behave in comparison to other subs. Third the sub still needs to be balanced somewhat (that is your point).
I tried to make it as realistic as possible and did a lot of testing. You can still detect the 212A with active sonar, as can be seen in the duels. The sub is kind of balanced out in the campaign with the low ammo count (only 13 torps) and the low speed (20 knots is official, but I would say 23 at least is realistic, maybe even 25).
At long range of the Seehecht just achived the world record for a torpedo with about 140 km acutually! So 75 km for the normal variant is ok. Also the sub needs to be played like that: hide and attack from pretty long range, and the Seehecht is good for that (but it is slower than the Mk 48 for sure).
Also one note: The project started as Typ 212, but it was cancelled as that. The restart was the 212A, so there was never a 212 and 212A is the right name.
Thanks for the feedback and I hope you have fun with the 212A and the Seawolf! I am doing some refinements with the rudders, the periscope and the sonar files and so on, might come with a later update!