1-10 is a weird meter for "explicit" in general, just because of nuance and blah blah, but it certainly makes you think. xD
personally, I don't find foul language to be a big deal, but some people might! I think that how a character talks about something/someone could be defined as more explicit than just saying f*ck in a sentence.
As for content/themes... eeeeee I may go with a 7.
I have my comic on M anyways, and also made a content warning as its own episode--mainly due to the fact that it's slow-paced and not much has happened in it... and I don't wanna scare readers away once they get further into it.
lolol
I like your teen rating of 15+... mine maybe that too? I'm used to seeing 14+ though, so idk. xD