First of all, quick question...
How is having someone become dependent on you and "addicted" to you on your list of positives? That strikes me as a blaring negative, and an extremely unhealthy relationship. Are you saying you (or the person you're reading for) WANT to become frighteningly dependent on the other person, or that you WANT the other person to become frighteningly dependent on you?
With that being said, since you're obviously not into the possibility of S&M-type stuff (since that was listed as a negative on your list) I can definitely say that I'd interpret this relationship to be extremely unhealthy and "bad," to use your word. Any number of possible scenarios could apply here, but all you need to do is take a look at your own list. You only came up with one possible positive (which I really think you need to reconsider as a "positive") and 4 possible negatives.
You already know the answer to your question. The possibility of a sexual relationship here is not a good choice, plain and simple.
On sight, 8 swords does seem like a negative card. But I've had some good experiences with negative cards, which has forced me to do a positive and negative interpretation on a card. For example, everyone thinks that 2 Cups = love and romance and comradery. And all that good stuf...WRONG! I've gotten 2 Cups when I am arguing with someone, because to be honest 2 cups = exchange of emotions among two persons, whether the persons hate, or love each other.
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To go further into the situation of this card...
Yes, the card is about me, concerning a man I met in April, but I haven't seen since. Recently, I just discovered his home, and perhaps work address and I was thinking about writing a short letter, only based on if the tarot cards could tell me if he would be interested in being contact with me, or not.
Oddly, enough when I did went to the library a month ago, and did tarot on a book called The Sexual Tarot Key (some book from the 1960s), I asked what is his sexual fantasy of me (and I didn't take this interpretation so seriously, because fantasies can be an imagination thing that doesn't mean you will want to act out...like a woman fantasizing about getting gangbanged by 20 men, but not actually trying to make it happen.)
And the reading said...
What are his deviant fantasy of me (5 swords)...
Degrading sex; penis destruction; vaginismus; dishonor; sexual loss; sexual deviation; rape, gangbang, threesomes. The conquering Phallus.
And I laughed at it at the time, because I have had fantasies of "degrading sex, rape and threesomes" when I fap-fap, but you won't be seeing me get in Craiglist's trying to find a man to pee on me. (I am not into that anyways. I am just trying to be funny." So I was like, meh, he got fantasies, so damn what, and I don't know which fantasy he has about me, since it could be any of the above. For all I know, he could fantasize about a threesome, but not rape. How am I suppose to know what he is into?
So yeah, I was shocked when I saw the 8 swords in the spread a few days ago. The whole spread was this (and please don't comment on the other cards, since this thread is not about spread interpretation. I just included in there so you can see the "big picture" of the 8 swords card. If you want to comment on the other cards, then private message me. Thanks)
His desire concerning me?... 9 Cups
What type of romantic relationship he wants with me?... Strength
What kind of sexual relationship he wants with me?... 8 Swords
Overall relationship he wants with me?... 6 Wands
When I met him months ago, he seemed like a gentleman. He didn't come off as a creeper, nor mean-spirited. Especially, since when we met, I was surprised that he was talking to talk to me, since he wasn't my type and I didn't think I was his type either (he was extemely Yuppie-WASP-y, and I am artsy-fartsy), so I became really shy from being shocked that he was trying to flirt with me, and oddly, he either took offense to my shyness, or he felt that I was too overwhelmed by the flirtation, so he backed off and left me alone. So, if he was truly rape-y, and a weirdo, he would be turned on by the "power" of me being shy and nervous?
Unless the 8 swords represents my shy-ness or fear (nervousness) and he wants to have sex with me in that state?
And I thought I was getting someone normal....until this reading. S&M sex...I am not down for, unless we are talking about it being like Madonna's "Justify My Love" music video, which sensual erotic with people dressing in S&M clothing. But "Hell no" with hogtie-ing, spankings until the skin blisters, and being a human toilette. No ma'am!!!