Iio that as a couple we can't see the line?

Me and my boyfriend both are aware that we have wild addictive personality's and have to try hard daily to rule ourselves hourly, because we can create all kinds of situations, and as we are pretty good enablers, things can get out there. We like situations, experimenting together, esp what toes the line inappropriate with an occasional taboo. It's hard to control in our head's and our environments due to the strong desire for devious acts and our complete uninterest in the things that are functioning around us normally. We always try to damper some of the strong wants we come across, for now, but we are always dealing with major trouble and always will.
Now as far as our conduct is toward each other is a constant compromise and work in progress. If allowed unleashed we would both probably prefer alot more illegal acts or taboo. We do take it to far and fight, back up and reflect, and we are learning how we are going to have to handle some things if we want to maintain a level of respect and not destroy the entire year and a half relationship, in 5 seconds flat. we cannot control always needing a situation that we are having to constantly change our perspective Tobe ok with a strange fetish or running damage control. When we are always recovering from some major, completely out of hand drawn out argument/game/incident that started over a little innocent exchange taken wrong or used as an advantage to try to do ulterior motive, every interaction can be an issue and potentially lethal.
My thing is, being we are going to keep this up, we have deviousness and sexual deveints at that, we may be working along now, but we have potential damage around every corner and we see that. So 2 questions:
1. we need the respect in tact but freedom to create variety. We have a lot of clashing sexual boundaries and a hard time directly communicating to each other, in the heat of the moment, to not get loud and rational. We have no one as a family member or friend so no one to step in or interfere. How far would we draw the lines together and when we are apart, (ex. are we to high risk that there should be a rule banning simple events, events such as taking a ride from a coworker of the opposite sex without both being present, for any reason period, simply for potential trouble) and what interactions do you see could possibly be the point of crossing into disrespect, if we were to do, if not now eventually? Agreeing to a foot fetish he has and rolling with it, but it turns into something else and may have uncomfy spinoffs, and you don't have the time to ask how other thinks and causing hurt-where could we have softened that. And fetishes, where is the line of appropriate if not shared.
2.he has a fantasy that he has tried to carry out already that backfired and was a mess, but is his intense important and most needed fantasy that even now is brought up and it is a daily request to share me with another guy and get to watch the guy stare at me and cum on me, esp on the foot. When he had set it up he was talking of going to motel and doing that with his best friend. I thought it was fantasy but it wasn't and he took me to motel to have sex. There was a fight and a change. I didn't get a pick in guy, bathing, I wasn't even romanced. The thing is, where is the line? Do I do it because he has to have but do different a d it'll be ok? Will it break us up? Will it open door later for us to try more?
I need what you would see as probably not worth the trouble ahead, what is no bad consequence just enjoy together, and what to avoid, normally. And then where can you see a line being tied where you could look the other way?