If it ain't on the page, it ain't on the stage.
Richard then would have no knowledge of who Jason's father is, especially if he has to ask if Lois ever loved Superman. Admittedly this is thrown into shadow by the fact that Lois lies. She lies to Richard and tells him that she never loved Superman. She also lies to Lex and tells him that Richard is the boy's father, but we all know that's not true. We know it from the get go, we don't even need to be told. So there is some wriggle room, but I'd say not much or else you're living in your own speculative imagination and not in the script.
My inclination was that nobody knew who Jason's real father was until he saves his mother with a piano. Richard is his own kind of hero and he acts toward Lois' love for Superman in the only way that a man who truly loves a woman can, by delivering her to her heart's desire. He may feel secure in the knowledge that Superman is an unrealistic guy to consider having a relationship with, but I doubt even that much and it doesn't matter.
For the record, I was raised by a man who is not my biological father, but I always called him 'Dad' even after I met my father as an adult. My biodad I call by his first name. Neither man seems to begrudge the other his history or status in my life.