Discussion in this thread has become very emotional and has deviated from a objective perspective.
Things would probably have chosen a different path if SAJunky and I had a conversation on a PM basis but it is at it is.
Here my personal wrap up:
Most of my important data (digital images) I could retrive from backup. Newer were still on the SD card of the camera. There is only a small gap of 3 months missing when I did not take too much photos. A large email archive has a major information gap with mails that I thought to be important. But up to now I did not miss any mail.
Quotes from professional DR services I regarded as too high for the "relatively" small data loss. Therefore I thought to give it a try for a DIY rescue operation and look how far one could get along with this.
This forum is full of very valuable resources - for the enlighted ones - and brilliant people are commenting and giving hints. And I have to compliment SAJunky who is really engaged to help people and investing a lot of effort for support.
In the recent case of the burnt diode in a 7200.7 his guidance was correct and led to a success if I interpreted the discussion thread correctly.
When I started I was enthusiastic about his great committment and was fully aware of an implicit DISCLAIMER: whatever comes out is completely my responsibility: It was me that did not backup, It was me that scrubbed the drive with ddrescue for 2 days until it reached a final copying speed of 0 bytes/s, and it was me to apply cryptic commands suggested by SAJunky. So any data loss or drive exitus is my fault. I am blaming nobody.
SAJunky definitely knows much more about the Seagate drives than me.
But this knowledge is still not enough yet for a deterministic rescue approach in my case. And additionally our drives seem to behave differently. So I fear that his findings do not necessarily apply to my drive. We both are hoping for substancial input but up to now we do get only warnings not to proceed with DIY things. This is somewhat disappointing.
But know you what: I understand those of you who would not like to issue a suggestion that finally might lead to OP's data loss - especially without a detailed diagnosis. Or maybe even worse leading to a successful data rescue that would animate lots of potential customers to try a DIY rescue who would then maybe screw up their drives completely because the situation is different than in the succesful cases. Not to forget to unveil the secrets of a very special technical knowledge acquired in many years or paid for.
The real reason why I am sort of giving up is that there is no progress of the operation and I see a completely irrational time invest from SAJunky and me. Every day I am thinking of how to get the data out of this shitty drive and I am looking in the internet in - even russian (Don't even know the characters) - forums for a potential hint. But there is simply nothing concrete what helps. The internet is opaque here. It is as if I reached the borders of a world.
So I feel guilty steeling SAJunky's time and I am fearing slowly to get mad about extracting data ("it must be doable!") from this drive. And although BlackST's comments are not so helpful as hoped for he made me think about what we are doing.
I have to stop now, take a break, sit back and acquaint with the idea that my data is lost it in its dark pyramidal grave and be glad that it is no modern 2 TB drive. Think of backup strategies and maybe return to ancient film photography. (Really my parents have still negative films from over 50 years ago)
Maybe I will just open the drive just to see if there is an optically visible damage, finally ceasing my quest or maybe I will wait for an intuition how to proceed.
Twenty years from now I will show my son the drive and tell him: on this are pictures when you were 3 years old

But don't beat on SAJunky. He is definitely a good guy! Thanks to him a lot!