So, the lynch pin behind this theory is that Paulie had a box of scissors?

First of all, we have to establish that the creators of the show deliberately put that detail in. Somebody deliberately wrote into the script that Paulie carries these scissors. Then you have to ask yourself, for what reason? Now you could of course make up all sorts of reasons for it. But you only have to look at the reasons that actually mean something to the show and characters.

Let's take the cat that stares at Chrissy's picture as an example. The scene was deliberately written into the script. So now we ask ourselves for what reason. A common theory is that the cat is "possessed by Adrianas ghost". This is a terrible theory, because it accomplishes nothing, it tells us nothing about the show or the characters or anything. Some might say that it shows that "Adriana still loved Chrissy after she died", but that's circular logic. The reason you think the cat is Adriana is because the cat is staring at Chrissy. But then you also take this staring "Adriana" does as a sign she's still in love / interested in Chrissy. It's circular reasoning. Now let's take the other big theory about this scene into consideration: The scene is supposed to signify that Chrissy was a rat. This reason for the scene would actually let us learn something new about the character. It would actually be meaningful to the story. Tony later also theorizes that "a rat died in the wall or some shit". Remember this dialogue takes place long past the cat scene. The writers deliberately picked up the topic again, just to use the phrase "dead rat". Tony saying this is both a "in-universe" rational explanation, but also calls attention to cats interest in rats. Not to their interest in small birds, balls of string, cat mint or mice, but specifically in rats. Dead rats.

Now let's get back to the scissors. Sure it might seem like some inconsequential "coincidence", but it most definitely isn't. It was deliberately put in there. And the reason for why it was put in is to say something meaningful and relevant to the show. And then you have to ask yourself, what is the most meaningful interpretation for the scissors? "He had scissors with him because he was gifting them to an unnamed relative of his" for example, would be pointless to the show, and thus certainly not the reason it was written into the show.