I've linked the relationship between my stepson and his real dad and now I'm in a real mess. Please help!?

My Stepson writes to his biological father all the time. He reads the draft to me before he sends it, but in the beginning his father never responded. I couldn't stand the thought of having his heart broken like that so I started writing responses as if I were his father (which I know now is a big mistake!). It's been going on for three years now, and he keeps asking to meet up with him. I don't know what I should tell him. I know it sounds crazy but I'm seriously considering having my best friend (who is a hollywood makeup artist) do me up with some prosthetics and just going through with the meeting. I'm an actor (which is how I met my friend). Would it be damaging to skit out a departure so I can end this charade? He's turning 22 next month, and he's thinking about getting married so I don't want to get the situation with his biological father all mixed up with his wedding and whatnot.