Just a partial answer here to one of the questions posed in the body (not in the title):
"Is it safe to assume that such marriages of marrying off a Christian
daughter resulted in their forced conversion to Islam, and that they
were not allowed to remain Christian?"
It was not always the case that the wife would convert to Islam, at least when the ...
I think the ancients did produce purple dye via admixture.
Various challenges with that approach (and purple dyes in general) likely affected its historical ubiquity or our perception of that ubiquity.
Regarding your specific sub-questions:
Though challenging, ancient humans have mixed dye components to create purple dye, however, more complex factors ...