I'm confused about the seemingly irrational prioritization or vagueness (?) relating to the "3rd precept" compared to 5th precept of the 5 precepts I am confused why in many versions of the 5 precepts I have encountered that the 5th precept is seemingly beneficial about "refraining from intoxicating drinks and drugs which lead to carelessness." but compared to this the 3rd precept is seemingly only about "refraining from sexual misconduct" or "refraining from sensual misconduct". 

It seems to me one is to refrain from the use of intoxicating substances but sexual activity of some sort is permitted? Why is some sexual activity permitted?

I've been confused about the 5 precepts because to me it seems possible that in some instances one can cause oneself more suffering through engaging in sexual activity than through using intoxicating substances e.g. a) if I engaged in an all day oral-sex marathon compared to b) if I for pleasure went into the garden and picked 2 leaves of Melissa officinalis and made cold-brewed tea with those 2 leaves using rainwater that I had collected (brewing time 2 minutes) and had a sip of that tea. 

To my knowledge option b) would be less suffering for me but wouldn't I be breaking the 5th precept ("refraining from intoxicants") if I did option b)? 
but if I chose option a) then according to some interpretations I would be keeping the 3rd precept ("refraining from sexual misconduct") but to me it seems I would be suffering more?

So why would it according to some interpretations of the 5 precepts seemingly be possible to keep the 5 precepts but seemingly cause myself more suffering than breaking that interpretation of the 5 precepts and choosing option b) and seemingly suffering less? 

If the 3rd precept is interpreted as meaning "refraining from sensual misconduct" then what does that mean one is to refrain from besides the "prohibited sexual acts" mentioned in the suttas? 

It seems that there would still be the "irrational prioritization" I described with option a) and option b) if "sensual misconduct" is defined only as the sexual acts that are explicitly prohibited as written in the suttas. 

If "sensual misconduct" means something more than the sexual acts that are explicitly prohibited in the suttas then what does it mean? It seems vague (?).      

If the 3rd of the 5 precepts is interpreted as meaning only "sexual misconduct" then is anything else prohibited besides what is listed as "sexual misconduct" in the suttas I know of.  

Why isn't the "3rd precept" of the 5 precepts  "I undertake the precept to refrain from sexual activity."?
In the Buddha's time, for the most part, children were married off to a suitable partner by their parents when the children came of age (DN 31; AN 4.55). Until the girl was married, she did not engage in sex and was "protected" by her family, per the wording in the 3rd precept (AN 10.176). The young wife went to live in the family or clan of the husband (SN 37.3). They had children and spent their lives attending to family and clan duties. The 3rd precept was spoken in this cultural social context. It was not spoken to reflect the sexual hedonism of birth controlled sterilized 21st century society. In summary, once upon a time, women got pregnant easily when they had sex, therefore they were looked upon as wives &amp; mothers rather than as sex objects and probably sex was engaged in relatively infrequently &amp; cautiously (to control and avoid pregnancy). Obviously, in the Buddha's time, only relatively few people (such as the upper classes) engaged in an all day sex marathons. Therefore, there is no problem with the precepts. The problem is not discerning and understanding how freaky and abnormal 21st century dystopian sexual norms are.