Is it sufficient to sprinkle the inner garment with water and wash the penis and testicles and the area around them before each prayer, given the intermittent discharge of pre-seminal fluid (madhy)? And is it permissible to touch the Mus'haf in this state?

If the emission of prostatic fluid (madhiy) is irregular, your ruling is that of a person afflicted with سلس (incontinence). You perform ablution (wudu') after the time for prayer begins and pray as much as you wish with that ablution until the time for prayer ends. It is obligatory to guard against impurity using a cloth. The obligation to pack the site of impurity is waived if doing so causes discomfort that is difficult to bear.

It is permissible to follow the Maliki school of thought regarding the non-obligation of ta'seeb (binding the area), as they only consider it recommended. They also excuse the impurity of madhiy if it is emitted every day, once or more, without your choice.

What you used to do, which was washing the penis and testicles because of madhiy, is sufficient. Sprinkling water on underwear due to doubt is required by some scholars. However, if you are certain that a specific place has been afflicted with impurity, it must be washed. If the impurity is unclear such that its location is unknown, the entire garment must be washed.

As for touching the Qur'an after purification (istinja') and ablution (wudu') for each prayer, it is permissible.