Should I Have a Threesome With My Boyfriend and His Friend?

Got this puzzle thrown at me while chit-chatting with some chics (chics say the darnest things) and thought to share....
Scam-dalous followers please feel free to bare your minds on this topic.

Ochuko (not real name) is a 28 yr old working class lady, she met this guy on a social network site, hungout a few times and started dating.
Initially it all seemed rosy, until recently when she started observing some strange things.
Her words
"1. I saw a marriage vow written in his handwriting, professing love to another woman. I kept it to myself. Shows  scanned copy from camscanner [for privacy,, I'm sure you guys don't expect me to show it here ;)].
I had even moved a few belongings into his house and go to work from his place. When I could stomach it no longer I confronted him and he denied. I haven't seen that jotter where he wrote it since then.
2. Sometime last week he said he would like to have one of his friends over for the weekend and we should have a 3some all weekend long. I replied jokingly by saying yes, but with another chic not a guy. He kept at it all week long and I knew he was serious. On Friday evening his friend came and I conveniently went back to my father's house. In other words, I had a lonely Val's day. No call from him. Nothing.
The thing is I love him and don't want to lose him. How should I handle this? What should I do?"

Readers what do you advice?