Waiting and continuing to research and have discussions is NOT a bad decision! To me it show a great deal of maturity. So many people, claim to have a "rock solid" marriage, jump into poly (or anything else that produces relationship stressors) only to have all the flaws that were so easily ignored previously highlighted and magnified. I tend to be the negative personality. My first answer is automatically wants to be NO, then I think on it for a few hours and, then I'm fine with it. I know this about myself, and I try to accommodate for it, so instead of saying NO upfront, I tell people I need to think about it and will get back to them in a few hours.
Counseling wouldn't be a bad idea. Not counceling to "save" a bad marriage, but to make a good marriage better. You have already identified a few issues that the two of you struggle with, start there. Why do both of you struggle with jealousies? Is it fear, someone's being neglected, too much social programing, etc. I'm not normally a jealous person, but when I'm feeling neglected or ignored, then I do get jealous. Even if you don't see a counselor, spend some time working on strengthening your communication skills between the two of you.