I agree with @iammilind that the translation of BG 7.11 you cite in your question is a bit misleading and changes the whole meaning or intent of your question. This by no means undermines Prabhupada's translation or purport.
Personally, I liked Shankaracharya's interpretation of the verse from here the most:
Commentary by Sri Adi Shankaracharya of Advaita Sampradaya:
7.11 I am the balam, strength, ability, virility; balavatam, of the strong. That strength, again, is kama-raga-vivarjitam, devoid of passion and attachment. Kamah is passion, hankering for things not at hand. Ragah is attachment, fondness for things acquired. I am the strength that is devoid of them and is necessary merely for the maintenance of the body etc., but not that strength of the worldly which causes hankering and attachment. Further, bhutesu, among creatures; I am that kamah, desire -- such desires as for eating, drinking, etc. -- which are for the mere maintenance of the body and so on; which is dharma-aviruddhah, not contrary to righteousness, not opposed to scriptural injunctions; bharatarsabha, O scion of the Bharata dynasty.
But I think what he is trying to say is that there exist regulative rules for sex life.
You're absolutely right! The verse is not giving anyone license to have unlimited sex with whoever one wants whether one is single or married. But Prabhupada is only partly right to equate "kamah dharma-aviruddhah" to mean chastity alone when it should apply to controlling all forms of desire - eating, advancing your career, increasing your bank balance, sex drive etc.
According to his Divine Grace Swami Prabhupada intercourse is only for procreation.
Yes, Shankaracharya agrees as well. He used the term "for the mere maintenance of the body" above. So by common sense, masturbation, reading or watching pornography, extra-marital affairs etc. these all excite the senses in wrong ways and are not really required for 'maintenance of the body'.
Madhvacharya also agrees. Commenting on the same verse, he says:
It is primarily the unchecked desires for sensual enjoyments that causes the diminution of piety and morality; but these desires are not detrimental if they are attuned to sanatana dharma or eternal righteousness. The Supreme Lord resides in all desires that are not contrary to sanatana dharma; but he never resides in any action that is contrary to righteousness.
According to the above interpretation, your title question:
Regulative principles for sex life
Regulative principles for life in accordance with sanātana dharma
Unfortunately, questions like this are very tricky to answer unless you specify the Hindu sect you belong to because different sects of Hindus follow different rules. E.g., eating fish in Bengal is a common practice (see quote below) and if you read Hindu epics like Rāmāyaṇa and Mahābhārata you will find some kings (kṣatriyas) having more than one wife which is no longer an accepted custom now and even the local law doesn't allow it.
E.g., according to this blog:
Like I have mentioned earlier most Bengali Brahmins especially those residing in West Bengal are non-vegetarians and fish is a staple diet. In fact, traditionally fish is not considered non-vegetarian by us. After fish, mutton has been the most popular dish - however owing to it's high price, its consumption is low. After mutton, it was duck's egg which used to be a popular egg item.
Assuming you are interested in knowing the ISKCON way of dhārmic life §, here's what they recommend:
How to Practise Krishna Consciousness at Home
» Everyday Life: The Four Regulative Principles
Anyone serious about progressing in Krishna consciousness must try to
avoid the following four sinful activities:
Eating meat, fish, or eggs. These foods are saturated with the modes of passion and ignorance and therefore cannot be offered to the
Lord. A person who eats these foods participates in a conspiracy of
violence against helpless animals and thus stops his spiritual
progress dead in its tracks.
Gambling. Gambling invariably puts one into anxiety and fuels greed, envy, and anger.
The use of intoxicants. Drugs, alcohol, and tobacco, as well as any drinks or foods containing caffeine, cloud the mind, overstimulate the
senses, and make it impossible to understand or follow the principles
Illicit sex. This is sex outside of marriage or sex in marriage for any purpose other than procreation. Sex for pleasure compels one to
identify with the body and takes one far from Krishna consciousness.
The scriptures teach that sex is the most powerful force binding us to
the material world. Anyone serious about advancing in Krishna
consciousness should minimize sex or eliminate it entirely.
If you are interested in what Hindu gurus of other sects say about what sex means or should mean for a married or unmarried person, read my answer to another question.
§ I don't subscribe to ISCKON, but for completeness I quoted their basic rules. If you don't subscribe to them either, do let me know and I'll update my answer with more "generic" rules.