Sinuses can definitely cause eye issues! If your ophthalmologist isn't open to that (because mine sure wasn't), consult an ENT (ear, nose, throat Dr.). There is definitely a connection. Two sinuses sit adjacent to your optic nerve(s). I too get that pressure and have to squeeze the same spot on the bridge of my nose.
Floaters are a retinal thing. Most are normal but of course mention it to your eye dr. and ask about it. They are supposed to clear up after some time but I have permanent ones too that really mess with my vision. I am turning 40 too and my eyesight is atrocious.
Good luck with everything!