I always just used condoms. I only had unprotected sex with women I was willing to have kids with at times we both wanted kids. Over 50 years old, no unwanted pregnancies and no STDs ever. Condoms also help a man last longer in bed, which can help make it more enjoyable for your lady.
I'm skeptical. Anything targeting signalling pathways seems likely to have consequences that aren't apparent from animal trials. I remember a few years back that MENT (trestolone, 7α-methyl-19-nortestosterone) was being investigated for use as male contraceptive, and one of the biggest issues I recall was that it caused really wild mood swings in a number of men. Admittedly, MENT is hormonal, but I don't think that issues it caused were anticipated; I think the profile looked much more promising than it ended up being.