From where I'm sitting, it looks like part of the problem is that you added more relationships into your life at a point when your existing relationship needed tending. Now your marriage still needs tending.
Your husband says he is ok with you dating someone else and he's happy with the status quo. It sounds like the status quo has a lack of intimacy. I suspect that's part of the reason you're not "feeling it" with your husband.
Relationships take active work. Left to their own devices, they tend to cool off. It takes effort to keep the intimacy alive.
I read an interesting article about that. The gist of it is that small tokens of physical contact build intimacy. It's not that you lose intimacy first, and then those small tokens start to fall off as a result. If you can make an effort to do those small tokens, then intimacy will increase automatically. Small tokens being things like holding hands in the car, resting your hand on his leg when you watch TV, smearing icing on his nose at a birthday party... just those sweet little things that couples do naturally when they're starting out and then forget to keep up. In other words, all that stuff that makes 8 year olds gag
That's just what I can see from here. You mention "other issues" in your marriage without going into detail, which is fine. But my suggestion is to deal with these issues, or at least try, before throwing in the towel. No relationship worth having comes without some effort. If you want to skip from relationship to relationship, you can, but it probably won't be very fulfilling. At least, if you put in the effort and it doesn't work out, you'll know you tried.
The jealousy is a separate issue completely and there's tons of info out there for dealing with it, so I won't go into that.