Will Allah accept me and not punish me for the sin of speaking with a married man and overstepping boundaries with him, after my sincere repentance? And am I wronging him by distancing myself from him, and will Allah punish me for the pain I caused him as a result of my distancing myself?

You must take the initiative to repent to Allah Almighty for what you have fallen into regarding the forbidden relationship, by cutting off this relationship immediately, regretting having done it, and resolving not to return to it. You are not wronging him by cutting off the forbidden relationship; rather, you are wronging yourself by persisting in it. Fear Allah and return to your senses, and increase your seeking of forgiveness. And know that Allah accepts your sincere repentance, and "the one who repents from sin is like one who has no sin."