Wasn't there an article a while back that suggested the DoF is roughly equal if you frame a subject the same way? I.e to frame a subject the same size with a 100mm lens as with a 50mm lens you'd have to be standing much further back and they balance out
Also - how can't your 85mm do f8? All lenses should do f8
Edit : this article - https://luminous-landscape.com/dof2/
Also - how can't your 85mm do f8? All lenses should do f8
Edit : this article - https://luminous-landscape.com/dof2/