You putting it in clearer terms is an opinion.
Since I have trouble remembering what I had for, what is our first meal of the day called, let me get back to what I remember as being he central thought---What is pleasurable can be a sin---all sins are harmful, physically, or emotionally.
Fine - with sins being anything harmful to oneself or another person the discussion is much less fun, though, as I think our moral systems differ too much.
I don't have a need for calling anything a sin. All that exists is part of the divine.
Whether something is right to do or not only depends on how one feels and thinks about it.
Adultery---a married person having sex with someone other than the spouse.
Fornication---2 who are unmarried having sex.
I am not saying it is impossible to love someone, and live with them without the license and the ceremony
There is no marriage ceremony in the Bible. When they got married in the OT, the man went into the woman's tent and hey were hitched if the woman consented.
Ah, so the problem is just the social construct of marriage. If people just never married they could all have relationships on their own terms and there would be nothing like adultery
(Just a lot of fornication instead.)
However, at least in my native language, one of the main translations for adultery can as well mean "having sex with another person than one's partner(s) while being in a not-open relationship", so it's used independently of whether one is married or not.
And I would think the same, what feelings get hurt doesn't depend on whether one is married or not. Therefore, your moral system seems to be not too concerned either with whether any actual harm gets done but rather with forbidding specific acts regardless of circumstances and consequences.
But back to the actual topic of the thread.
So maybe if I clarify a bit...
I feel like I need a spiritual path that:
1. Focuses on self-actualisation
2. That is more 'grey' than either dark or light.
3. That focuses on maximising pleasure for all and minimising pain for all (not just for myself)
4. Has a deity I can work with as an archetypal identification
I feel like I have explored them all out there and none really are appealing to me. I will keep searching, however...
In that case, why not creating a religion yourself? Either with your favorite deity of those available, or with a one you made up yourself?
That's basically what we LHPers do, and why I still think that it would be a good choice in your case.
One of the least "dark" LHP-religions (or whatever you want to count it as) was already brought up: Discordianism.
Have you explored that one already?