I used to have a shallow saddle, but after an labial bruising incident (ouch) and experimenting with padded shorts, a gel cover, and saddle angles, I now have a well-padded cutout saddle (Amazon for £15ish). The cutout/hole makes SUCH a difference, would highly recommend if you have an outie vulva. I also have seatpost suspension and springs, I like it bouncy. (I don't have pelvic floor issues yet, mind.)
Sorry your brother is a bit of knob! Have you asked whether it's 'correct' for women, not short men? Women's legs are proportionally shorter. I too prefer to be able touch the ground with my toes - it feels safer for traffic lights and emergency stops. I've found they put saddles higher in the UK than the rest of Europe. When it's too high I overextend my leg when the pedal is at the bottom.
Sounds like you've found a great bike shop/fitter though - good sign that they're letting you try a saddle before you buy. Are their suggestions re handlebar and seatpost to resolve reaching/body angle issues? Because it sounds like the frame is just too long for you. I had a similar problem with a 2010 Dawes women's bike. It felt like a men's frame length, and my arms just aren't that long, most of us have proportionally shorter arms. I've switched to a Dutch brand (Gazelle) - I've found Dutch brands better at women's frames.
(Yes, I got very annoyed trying to resolve my bike issues and spent a lot of time reading women's cycling blogs/forums...)