In my experience, the dojocho/chief instructor sets the tone and others will fall in line.
Yes. If the people teaching assume women are fragile little things, at least until proven otherwise, all the others will follow.
Actually I think it's quite naturally that women and men are treated differently in the aikido dojo. We don't treat the sexes the same in normal life. That's in our culture. It follows into the dojo. But if everyone involved knows that we should strive at treating the sexes the same on the mat - that does not mean treating all individuals the same - that's a major breakthrough.
People always assume (within the same kyu rank) that the males have senority over me- even if they JUST got promoted to that rank.
I'm not a big fan of rankings... but this is a good reason to have them. If you didn't have a rank, everybody would probably act like if pretty much all the guys were your seniors. Now rank is something official, making side stepping more difficult.
Being the only one in "the other locker room" isn't always fun. That's for sure. Probably your best option is finding another dojo, where you won't be the only woman.
You could do a little investigating without making hard decisions beforehand. Cut down on training at your regular dojo, or take a little leave (if people ask, you just don't have the time, or you have other priorities at the moment). Visit other dojos. Watch classes, then try training a class if it looks like fun. If a little bit of dojo hopping makes you decide your old place isn't too bad after all, that's also a good outcome.