I think you need to find a neuro opth or behavioral optometrist who understands visionand brain trauma. I have a great one in Minneapolis. I am sure there are others who could recommend where you are. I was told my lack of eye teaming horizontally can be much improved by prisms and vision therapy (maybe get rid of that prism!) but that my vertical lack of teaming (working together) could be permanent. I have a both an up and down and a side to side prism.
It is really hard work to keep the eyes working together, even though you may not perceive it. It takes cognitive space away from other activities.
I hope you can get the good help you need!!!!
I think I would avoid on line prisms unless they were prescribed. You don't want to make things worse.
Take care.