Maybe if you explain to him about the pyo that will make up his mind? Also, the KC have urged people not to breed anymore staffies as there are SO many in rescue, so really only the most experienced and responsible within the breed should be contemplating it.

I don't mean to be rude, but am I right in understanding he left his in season bitch tied up outside a shop unnattended while you both went in? If so, not at all advisable.

You're a good friend asking advice on his behalf.