Does the intentional emission of semen after pressing on the penis—subsequent to waking up from a wet dream and finding no wetness—invalidate the sixty consecutive days of fasting for expiation?

It appears that the semen was released during sleep but did not exit until after waking. This does not invalidate the fast. It is stated in Kashshaf al-Qina': "By it (ejaculation) is established the ruling of puberty and breaking the fast for one who kissed, or repeatedly looked with desire, and the like, but not for one who had a wet dream." However, if semen exits while awake without desire, it also does not invalidate the fast. Based on this, your fast is valid and you do not owe any make-up days.