Yes, no hard border was wanted by both. Initially, the UK Govt said they would use technology on the border. This bespoke idea fell apart as nothing sufficient exists. If it did, it would have been applied at the Swiss and Scandinavian borders by now. People in the UK said the technology will be invented in the future, but to mitigate the risk it is not, the backstop was agreed which is the solution for the historical political problem you describe and the internationally recognised Good Friday agreement. The EU are already doing something they don't want as it is still an uncertainty as its still not fully resolved. This was them agreeing to something bespoke and bending their rules in my opinion. The fact that MP's, including pro leave, in Parliament voted it down is not the EU's fault. Maybe that was the error in judgement you mentioned, but surely that is the Govt's fault for not having an idea of the many fractions that exist within their own party.
Your example of the German politician is interesting. I agree that the Govt's negotiating tactics and rhetoric has not helped at all.
Pooled sovereignty - I think this is where you and I would disagree. Pooling it for 14% of our laws to service and function a sophisticated customs union and single market does not bother me. I look at it in the way that in all aspects of our lives, from birth till death, we have to live by other peoples rules. School, work, your boss, the insurance company, your bank, your mortgage provider, DVLA, ABTA, Easyjet etc etc. I don't have a say in their rules. Yes, I could change providers, but they will still have rules. Whats a few more made by people i don't know or will never meet.
Your three questions - again, I look at things differently and I will never change your mind. I know that. But I personally would vote/say yes to all three.
However, looks like there has been more developments this morning with the extension request. I am beyond confused !