I haven't played this side story yet, but it appears to have NTR so you are probably right to feel stressed/guilt. I will say for the main game though, pursuing Suni (although the neutral route doesn't have a true epilogue) and if you are a patron, the Mallory route is complete with different endings, and one of them may accommodate your male ego.
I personally think you should quit playing the games, but if you still enjoy them then I really think you should understand the context a bit more. To this day in more traditional countries women are still treated as 2nd class citizens, sole purpose and fulfillment to serve their husbands as wives and mothers, but even then their husbands could still legally beat and rape them.
In FDW, men are 3rd class citizens and have about the same rights, intelligence, and strength as a child would in our world, so you should feel lucky if any futa respects and desires your companionship at all. When a woman is inseminated she makes a child and you can raise it in your image. In FDW, when a man is bound and inseminated the futa can raise the man in her image also.
I'll admit it is sad to see one's intelligence go after binding, but it is the necessary sacrifice to achieve unconditional love in the FDW universe, for both the man and the futa, and realizing this fact actually made me cry after one of the Mallory endings, out of bittersweetness, and for how it was so beautifully portrayed.
Like Demetria quotes in the game "'Love is the wisdom of the fool and the folly of the wise' and men are fools." Good luck my friend.