Can floaters be caused by a sinus problem above the eyes or near the nose where eye sockets connect? I've had pain in that corner for two years now.

Unlikely. Floaters are generally caused by small opacities in the vitreous gel contained within the eye (like a holiday snow toy). They are often a part of aging or can represent early signs of a retinal tear. Sinus problems usually are noted below or above the eye where the frontal and maxillary sinuses are located. Inflammation here can cause aching.
No. Floaters are a result of an effect of changes to collagen in the vitreous jelly/ humor which is inside the eye. Perhaps a raging infection of the ethmoid sinus pressing on the eye might be able to cause an alteration in the vitreous. Sinusitis can cause peri ocular discomfort and pain interpreted by some patients as pain in the eye.