I married my Supervisor. I've written extensively about that relationship on this site, and you can probably find most relevant posts by doing an advanced search. But to answer your questions,
1. We are not still together. We are divorced.
She calls me about once every six weeks to invite me to dinner, or when she needs someone to take her somewhere, but otherwise, no. I've moved on.
2. My partner and I were almost perfectly matched from a social, intellectual, and world-view standpoint. We communicated very well regarding the things we had in common (Te), and very poorly for the things we did not (Si). Overall, SLI's are not that talkative. To her credit, she never tried to tell me what to do, and that is probably why the relationship lasted as long as it did. Other than that accommodation, she never really changed her approach to me, despite my requests and complaints and our many mutual therapy sessions.
3. Our marriage lasted over fifteen years. The "breaking point" came when I came home one day and found a moving van in front of the house. I said, "Helen, what's going on?" She, moving furniture into the van, said "I'm leaving." I wondered if she was leaving right now to move the furniture into a storage locker because she had bought all new, so I asked "Where are you going?" and she said "I'm not telling you", and then I realized that she wasn't just leaving the house for an afternoon trip, she was leaving the marriage.
My present feelings on Supervision are that the Supervised always looks up to the Supervisor, and the Supervisor always thinks the Supervisee is an idiot.
I tested this once after she left. My son is also an SLI, and when he was in his low teens (I can't remember exactly when this happened), we were driving somewhere in an S-class Mercedes and I asked him if he thought I was an idiot. He instantly became uncomfortable and said nothing. I tried again. "Son, do you think I make bad decisions?"
This time he replied. He said, "Dad, all of your decisions are bad."
How he came to this conclusion, when he was aware that his mother and I started our marriage with nothing (she was actually in debt) and I had been running an increasingly profitable business since he was born, is beyond objective reconning. It is not, however, beyond the purview of Socionics.
In my opinion, these feelings are ingrained and can be hidden or ignored for a while, but not changed.
*EDIT* I know you didn't ask for comments on your present relationship, but let me tell you a short story example about EII's and SLI's.
My ex-wife's sister is IEE-Ne, and my ex-wife is SLI-Te, as is my son (This is a non-optimum match of dual sub-types). Both my ex-wife and my son think the IEE-Ne is crazy random and they actually can't stand to be around her very much, but I've seen them all work together and I've never had any doubt that they mesh incredibly well because of their shared values. I have a bookkeeper who is IEE-Fi, and she and my SLI-Te son get along better than any two humans I've ever seen (despite their age differences, which actually aren't seen by socionics functions). And SLI's are not the easiest people to get close to, since they hoard their resources, which include their wealth, their space, and their time.
After my divorce, I found an IEE-Ne guy and told my wife she should consider him. She visited him for a weekend to help him with a party he was hosting, and when she returned, I asked her how it went. She said, "He's pretty scattered.", which meant No. So sub-types matter a lot.