All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
It seems that all the questions of the brother relate to the criterion of prohibitions and their relation to the harm of the body, society and so on. You have to know that anything that causes harm is prohibited as the Prophet said: "There should be no harm nor reciprocal harm." [Maalik] However, even if the reason for a prohibition is the existence of the harm, the harm should not be taken as a criterion for that. It might be that there is much harm in a given matter but people are unaware of it. Contrarily, another matter could appear as if there are many benefits for the people in it but in reality its harm is greater than its benefit. Allaah has not forbidden anything except that there is harm in it and did not ordain something except that there is good in it. However, this fact could be overlooked by the individual himself. Therefore, the criterion for prohibition is what Allaah has prohibited with a clear explicit or implicit text or revealed to His Prophet to prohibit. This can only be known by studying the religious texts and their principles.
Allaah knows best.