1. Isaac is a pro athlete. He's in the town where his team plays...
2. Lorenzo? Explains when he runs into Lacey at the bar that he got a job at the bank in the town...
3. A plot device...

The plot needed them there, so they're there...
Lorenzo and Barty showing up at the apartment...
Lorenzo says he got a strange message from an unknown number giving the address and telling him to go see Lacey.
The MC realizes and says something like I know a setup when I see it, this has Jared written all over it...
Similar with Barty, and I'm willing to bet Isaac got a similar message giving him Lacey's address.
I think it's more than possible that Jared is the one who filmed and posted the MC v Isaac bar confrontation...
As for the rest, you're seeing/expecting the worst of Lacey while ignoring all exculpatory evidence to the contrary.
It's understandable, but it's primarily speculation on your part based on how you perceive Lacey's actions/intent, similarly to the MC, which I don't think is a coincidence. My hypothesis is people read the MC's narrative as some form of or close to the "truth" about the story without even realizing it. I think it's called suggestibility in psychology. In this case, a reader is internalizing the MC's thoughts/feelings about Lacey, influencing the reader's opinion, instead of viewing all evidence critically.