I'm not even going through a recent breakup, it's been like a year and I browse this subreddit occasionally to chime in and help others. You're 100% spot on, and this applies to women too.
Realizing these points is key.
My ex would follow various male influencers and like their pics. Some people would tell you it's benign, that it's just Instagram and pictures, but I say fuck that it isn't at all. It's the equivalent of openly checking people out on a date in my opinion. I don't do it, in fact it felt icky to do so, I expect the same from anyone I'm seeing. It's courtesy.
My ex kept in contact with a childhood friend that she fucked for two years a while before dating me. I don't have issues with people fucking other people when they're single obviously, especially if they're not fucking everybody in sight. I put my foot down and said she should cut contact with this guy, unfollow on Instagram etc, she pulled the insecurity card on me. I didn't budge. It's not cool. I cut contact/blocked previous hookup/flings/people I was involved with before her no matter how close I was. I expect the same.
If your ex/person you're seeing is doing the above and you feel uncomfortable, you're not insecure you're human. Absolutely the person you're with should make you feel secure. I'm also not a particularly insecure individual, sure I have my hang ups, but I'm not crazy. I was gaslit to think that I was, which wore off about a month after the breakup, which felt damn good.
I think actual love is enough, like real dedication, but that's super hard to come by in the real world.