I have not read the Philokalia, but I certainly want to in time. I am new tho the Jesus Prayer as well, and am just now beginning to practice this discipline. But a couple of points I would like to make, although they are probably influenced heavily by my past Protestantism.
1. As far as the Philokalia being scary at parts or dangerous to read:
I would say the same thing about the Holy Bible. The unbelievers will scoff at its mystical truth, and perhaps even be offended by the severity of judgment that they come across in the Sacred Texts. But the one who loves Our Lord will always be comforted and edified by holy truth; for even that which is fearful is that which drives us to repentance, and thus we as Christians are grateful for it. So, I imagine the same applies to all the sacred texts of the Holy Fathers as well.
2. As far as the Jesus Prayer being dangerous to pray while going to sleep:
Prayer is communion with God. Through Baptism and Chrismation we are anointed with Holy Spirit, and exorcised of all demons. We renounce Satan and all of his works in the sight of the Holy Mother Orthodox Church. We therefore become God's children by grace, and thus we should never fear to come to Him in sincere prayer. We should cherish prayer, be reverent in prayer, and view prayer as what it is- communication with, supplication of, and praise to Our Lord. I think it is better to fall asleep with the Name of Our Lord on our lips and in our hearts than to drift off into another consciousness with unholy thoughts in our heads.
But I do not want to contradict my Ethiopian Orthodox brother, because I am very new to the Faith. These are just my very humble and neophyte opinions.