We are sorry to hear of your anxiety with preparation for the mikveh.
Especially when preparations are begun during the day, their duration is flexible. Though the
chafifah overall should take at least a half hour, the bath need not be that long, so long as there is enough time to clean properly and soften any scabs.
It seems that most of your difficulties are tied to the
Friday night timing of your immersions. We suggest you consult your physician about using hormones to slightly
adjust your cycle. If you already use a
hormonal contraceptive, you can shift your mikveh night by slightly manipulating the pills. If you are not using hormonal contraceptives, a short course of progesterone can help you shift.
Please write back with any further questions.