It's hanging up in the garage looking unloved. Still can't get the BB out despite the tool ( and I'm not referring to me). I know the direction it's going in and have most of the parts for it but I'm missing one thing....."time"....The rarest of Retro parts Just keep badgering me as I'll get around to it......"One day"
I think you need to apply more leverage.
Like a big long pipe or something over the wrench handle.
Fashion something so that the jaws don't slip off as previously suggested.
And also, those workstands can be a bit flimsy/flexy when applying loads of force.
I'd put the frame directly on solid ground (on carpet like).