A good habit to do is to review what fake tickets look like. The use of PayPal is a good options since it can protect both the buyer and the seller. I have seen, and used tickets that neither look like standard season hard tickets or TM printouts. They look like they are tickets to the enter the Hall. Some ST holders have access to extra tickets and they are box office printouts. But you have to know how to ID the fakes there too. I was so skeptical the first time I almost offended the STH. He made me take a photo of his drivers license the first time. I didn't understand why then, but I do now. In the end I developed a very good contact and has sold me excellent tickets (same strange tickets) to games I wanted them. I know where his seats are and he never charges me a premium. He even mailed me the hard copy of his season ticket for the home opener in 2015 as a souvenir.
As for going alone...done it. Do it! Just drink more beer! LOL.
I bought 4 tickets off CL for this game. The exchange was/is a nightmare. My contact didn't have any tickets to spare. But I found a local ad, did my homework, have his patriots account number and other contact info so if there are issues. I expect none.
I hope you get to the game. I wont be 3 rows off the field like I was in 2014, rather I'll be 2 rows from the top this time. But I'll be there with a daughter that is just as excited! And that doesn't have a price tag.