I have mulled it over and read some more information about SLEs and LSIs and agree that he was a SLE-Se, instead of a very, very unhealthy ESI like I first thought. It explains his vindictive behaviour, him claiming my resources as his own, and the overall uncomfortable feeling I experienced with him pressuring me, just like what I feel around the SLE-Se dad of my high-school friend. When I first encountered him I had discounted the possibility of him being an SLE, because he was looking for a serious relationship, instead of an uncommitted hook-up.
Him being an SLE-Se also explains his terse response to my heartfelt apologies, whereas actual ESIs would have engaged emotionally by reprimanding me for my bad behaviour or forgiving me, instead of merely stating that they missed respect from me. And they sure as hell wouldn't play along, just to stand me up for a second time, in order to get back at me.
It seems that I was projecting my desire for meeting a gay ESI interested into me. He also lacked that fairchild-feeling that the previous ESIs I dated radiated, nor the tacit wishing well-vibe of my ESI friends. Instead he exuded forcefulness and forcefulness alone. It seems that my ILI, LSI, and other friends were totally right to warn me against him, and that I indeed dodged a bullet after all.
It feels like a weight has dropped from my shoulders now that I understand what went wrong, and that it wasn't really my fault, nor that I could have reasonably averted it. It should have been a telltale sign to me that his behaviour was so alien to me, and that he thus couldn't possibly be my dual. It generally took me a month or two of reflecting on his behaviour to even make sense of it, so incomprehensably vengeanceful he acted from my perspective.
Thanks for your advice, guys! It has helped me tremendously!