What is the ruling on fasting, and what is incumbent upon one who fondled another male's penis sexually during the daytime in Ramadan after puberty and ejaculated?

What you did was an atrocious act and a violation of the sanctity of the month. Since you have repented, we ask Allah to accept your repentance, for sincere repentance erases what came before it, and one who repents from a sin is like one who has no sin. If semen was discharged due to the foreplay you mentioned, your fast is invalidated, and you must make up for it. You are not obligated to offer expiation according to the majority of scholars, as long as no penetration occurred.