The existing situation is bad in at least two ways. First, your lover is deceiving her husband and the father of her child who is, as you put it, a reasonable man. He deserves better. If his wife does not love him, he should know this and have a chance to plan the rest of his life in light of this knowledge. Second, your affair is likely to come to light at some point, and this might have much worse consequences for all involved, including the child, than a frank confession.
I see two potential ways out of the problematic situation. First, you can agree to end the affair. You can still write each other, see each other occasionally, perhaps, but you should then try to meet the husband and make quite sure that there is no return to a romantic relationship. If this is unworkable, this first option would call for a complete end of the relationship.
Second, you could agree to marry each other after a divorce. You write that this was not workable earlier "because of the social issues". I don't know what social issues these are (feel free to write in more detail about them), but if you really love each other, then perhaps it's worth working really hard on breaking through them.